This section has two verses.

Titus 2:7-8
7 In all things shewing thyself a pattern of good works: in doctrine shewing uncorruptness, gravity, sincerity,
8 Sound speech, that cannot be condemned; that he that is of the contrary part may be ashamed, having no evil thing to say of you.

We will begin with the Barclay Commentary.

THE CHRISTIAN CHARACTER
5. THE CHRISTIAN TEACHER
Titus 2:7–8

And all the time you are doing this you must offer yourself as a pattern of fine conduct; and in your teaching you must display absolute purity of motive, dignity, a sound message which no one could condemn, so that your opponent may be turned to shame, because he can find nothing bad to say about us.

IF Titus’ teaching is to be effective, it must be backed by the witness of his own life. He is himself to be the demonstration of all that he teaches.

(1) It must be clear that his motives are absolutely pure. The Christian teacher and preacher is always faced with certain temptations. There is always the danger of self-publicity, the temptation to demonstrate one’s own cleverness and to seek to attract notice to oneself rather than to God’s message. There is always the temptation to power. The teacher, the preacher, the pastor is always confronted with the temptation to be a dictator. Leader he must be, but dictator never. Titus will find that people can be led, but that they will never be driven. If there is one danger which confronts the Christian teacher and preacher more than another, it is to set store by the wrong standards of success. It can often happen that those who have never been heard of outside their own sphere of work are in God’s eyes far more successful than those who have become household names.

(2) He must have dignity. Dignity is not aloofness, or arrogance, or pride; it is the consciousness of having the terrible responsibility of being the ambassador of Christ. Others may stoop to pettiness; Titus must be above it. Others may bear their grudges; he must have no bitterness. Others may be touchy about their status; he must have a humility which has forgotten that it has a place. Others may grow irritable or blaze into anger in an argument; he must have a serenity which cannot be provoked. Nothing so injures the cause of Christ as when leaders of the Church and pastors of the people descend to conduct and to words unworthy of Christ’s servants.

(3) He must have a sound message. Christian teachers and preachers must be certain to pass on the truths of the gospel and not their own ideas. There is nothing easier than to spend time on side issues; but Titus might well have one prayer: ‘God, give me a sense of proportion.’ The central things of the faith will last him a lifetime. As soon as he becomes a propagandist either for his own ideas or for the interest of a particular group, he ceases to be an effective preacher or teacher of the word of God.

The duty laid on Titus is the tremendous task not of talking to people about Christ but of showing Christ to them. It must be true of him as it was of Chaucer’s saintly parson in the Canterbury Tales:  [knowing that Chaucer uses strange spellings of words]

But Cristes love, and his apostles twelve
He taught, but first he folwed it him-selve.

The greatest compliment that can be paid to a teacher is to
say of him: ‘First he wrought, and then he taught.’ ~Barclay Commentary

Now to the other commentaries beginning with the general and going to the specific.  We will begin with the Matthew Henry Main

5. With these instructions to Titus, respecting what he should teach others - the aged men and women, and the younger of both sexes (Titus himself probably at this time being a young man also), the apostle inserts some directions to himself. He could not expect so successfully to teach others, if he did not conduct himself well both in his conversation and preaching.

(1.) Here is direction for his conversation: In all things showing thyself a pattern of good works, Titus 2:7. Without this, he would pull down with one hand what he built with the other. Observe, Preachers of good works must be patterns of them also; good doctrine and good life must go together. Thou that teachest another, teachest thou not thyself? A defect here is a great blemish and a great hindrance. In all things; some read, above all things, or above all men. Instructing others in the particulars of their duty is necessary, and, above all things, example, especially that of the teacher himself, is needful; hereby both light and influence are more likely to go together. “Let them see a lively image of those virtues and graces in thy life which must be in theirs. Example may both teach and impress the things taught; when they see purity and gravity, sobriety and all good life, in thee, they may be more easily won and brought thereto themselves; they may become pious and holy, sober and righteous, as thou art.” Ministers must be examples to the flock, and the people followers of them, as they are of Christ. And here is direction,

(2.) For his teaching and doctrine, as well as for his life: In doctrine showing uncorruptness, gravity, sincerity, sound speech, that cannot be condemned, Titus 2:7-8. They must make it appear that the design of their preaching is purely to advance the honour of God, the interest of Christ and his kingdom, and the welfare and happiness of souls; that this office was not entered into nor used with secular views, not from ambition nor covetousness, but a pure aim at the spiritual ends of its institution. In their preaching, therefore, the display of wit or parts, or of human learning or oratory, is not to be affected; but sound speech must be used, which cannot be condemned; scripture-language, as far as well may be, in expressing scripture-truths. This is sound speech, that cannot be condemned. We have more than once these duties of a minister set together. 1 Timothy 4:16 [see Lesson] , Take heed to thyself, and to thy doctrine: and, 1 Timothy 4:12 [see Lesson] . of the same chapter, “Let no man despise thy youth, but be thou an example of believers in word - in thy speech, as a Christian, being grave, serious, and to the use of edifying; and in thy preaching, that it be the pure word of God, or what is agreeable to it and founded on it. Thus be an example in word: and in conversation, the life corresponding with the doctrine. In doing this thou shalt both save thyself and those that hear thee.” In 2 Timothy 3:10 [see Lesson] , Thou hast fully known my doctrine and manner of life (says the same apostle), how agreeable these have been. And so must it be with others; their teaching must be agreeable to the word, and their life with their teaching. This is the true and good minister. 1 Thessalonians 2:9-10. Labouring night and day, we preached to you the gospel of God; and you are witnesses, and God also, how holily, and justly, and unblamably, we behaved ourselves among you. This must be looked to, as the next words show, which are,

(3.) The reason both for the strictness of the minister's life and the gravity and soundness of his preaching: That he who is of the contrary part may be ashamed, having no evil thing to say of you. Adversaries would be seeking occasion to reflect, and would do so could they find any thing amiss in doctrine or life; but, if both were right and good, such ministers might set calumny itself at defiance; they would have not evil thing to say justly, and so must be ashamed of their opposition. Observe, Faithful ministers will have enemies watching for their halting, such as will endeavour to find or pick holes in their teaching or behaviour; the more need therefore for them to look to themselves, that no just occasion be found against them. Opposition and calumny perhaps may not be escaped; men of corrupt minds will resist the truth, and often reproach the preachers and professors of it; but let them see that with well-doing they put to silence the ignorance of foolish men; that, when they speak evil of them as evil-doers; those may be ashamed who falsely accuse their good conversation in Christ. This is the direction to Titus himself, and so of the duties of free persons, male and female, old and young. ~Matthew Henry Main

Now to the Matthew Henry Concise. This commentary covers verses 1-10.
 
 Old disciples of Christ must behave in everything agreeably to the Christian doctrine. That the aged men be sober; not thinking that the decays of nature will justify any excess; but seeking comfort from nearer communion with God, not from any undue indulgence. Faith works by, and must be seen in love, of God for himself, and of men for God's sake. Aged persons are apt to be peevish and fretful; therefore, need to be on their guard. Though there is not express Scripture for every word, or look, yet there are general rules, according to which all must be ordered. Young women must be sober and discreet; for many expose themselves to fatal temptations by what at first might be only want of discretion. The reason is added, that the word of God may not be blasphemed. Failures in duties greatly reproach Christianity. Young men are apt to be eager and thoughtless, therefore must be earnestly called upon to be sober-minded: there are more young people ruined by pride than by any other sin. Every godly man's endeavor must be to stop the mouths of adversaries. Let thine own conscience answer for thine uprightness. What a glory is it for a Christian, when that mouth which would fain open itself against him, cannot find any evil in him to speak of! ~Matthew Henry Concise.

Here is something from the Biblical Illustrator:

In all things showing thyself a pattern
A good example

Having propounded the several precepts fitted to all ages of men and women, the last whereof was unto young men, our apostle here inserteth a precept unto Titus himself, whence it is probably gathered that Titus was now a young man, as Timothy also was, in the same office of an evangelist; and being a minister, in him he closely again instituteth every minister, notwithstanding he hath been most ample in that argument, as though ministers could never sufficiently be instructed.

In these two verses we will consider two things.

1. A precept.

2. An enforcement of it.

I. The precept is, That Titus show himself an example to others. For as all the persons formerly taught, so more especially the last sort, namely, young men, for the slipperiness of their age need the benefit of good example as well as good doctrines and counsel. And this exhortation is enlarged by setting down wherein Titus must become an example, which is done, first, more generally, “in all things,” we read it, “above all things”; others, “above all men,” which readings may be true, and grounds of good instruction, but I take the first aptest to the place. Secondly, by a more particular enumeration of shining virtues, as

1. Uncorrupt doctrine.
2. Good life fruitful in good works; and these not one or two, or now and then in good moods, but there must be a constant trading in them throughout a grave and pare conversation.
3. There must be joined gracious speeches and words, for I take it fitliest interpreted of private communication, described by two necessary adjuncts.

1) It must be wholesome.
2) Unblameable, or not liable to reproof.

II. The enforcement of the precept is taken from the end or fruit of it, which is twofold.

1. Shame.
2. Silence to the withstanders and opposers.

And thus the general scope of the verses is as if he had more largely said, “That this thy doctrine, O Titus, thus aptly applied to all sorts of men, may carry more weight and authority with it, see thou that (considering thou art set in a more eminent place, and clearer sun, and hast all eyes beholding and prying into thee) thou show thyself a pattern and express type wherein men may behold all these graces shining in thy own life: let them look in thy glass, and see the lively image of a grave and pure conversation, which may allure them to the love of the doctrine which thou teachest: let them hear from thy mouth in thy private conferences and speech nothing but what may work them to soundness; at the least, keep thou such a watch over thy tongue, as that nothing pass thee which may be reprehended [find fault with], and hence will it come to pass that although thou hast many maliciously minded men, seeking by all means to oppose thy doctrine and life, and to destroy the one by the other, these shall either be put to silence and have nothing to say, or if they take boldness to speak anything, it being unjust, the shame shall be removed from thee and fall justly upon themselves; and all the reproach shall return home to their own doors.” ~Biblical Illustrator

Now to the specific commentaries.

Many commentaries put this verse in two parts:

1] In all things shewing thyself a pattern of good works:
2] in doctrine shewing uncorruptness, gravity, sincerity.

However for our use, I will break it out as Barnes Notes:

1] In all things showing thyself a pattern of good works.
2] In doctrine.
3] Showing uncorruptness.
4] Gravity.
5] Sincerity.

1] In all things showing thyself a pattern of good works.

In all things showing thyself a pattern of good works - Not merely teaching others, but showing them by example how they ought to live. On the word rendered “pattern” (τύπον tupon, type). ~Barnes Notes

In all things showing thyself a pattern - As the apostle had given directions relative to the conduct of old men, Titus 2:2, of old women, Titus 2:3, of young women, Titus 2:4, and of young men, Titus 2:6, the words περι παντα, which we translate in all things, should be rather considered in reference to the above persons, and the behavior required in them: showing thyself a pattern of good works to all these persons - being, in sobriety, gravity, temperance, what thou requirest others to be. ~Adam Clarke

In all things showing thyself a pattern of good works - It was not enough for Titus, and so neither for any other Gospel minister, to deliver out sound doctrine, and to exhort persons of different ages and sexes to the things which become it, but he should through the whole of his conversation be a pattern of every good work unto them; for they that are the shepherds of the flock, are not only to feed them with knowledge, and with understanding, but to be ensamples to them, as well as they who are under their care ought to walk, as they have them for an example. ~John Gill

2] In doctrine.

In doctrine - In your manner of teaching; notes, 1 Timothy 4:16. ~Barnes Notes

Quoted verse
1 Timothy 4:16 [see Lesson]
Take heed unto thyself, and unto the doctrine; continue in them: for in doing this thou shalt both save thyself, and them that hear thee.

In doctrine showing uncorruptness - Mixing nothing with the truth; taking nothing from it; adding nothing to it; and exhibiting it in all its connection, energy, and fullness. ~Adam Clarke

In doctrine, showing uncorruptness, gravity, sincerity - the apostle here either returns again to his advice about doctrine, that it should be delivered out pure and incorrupt, free from error and heresy, and every mixture and invention of man's; and with all gravity of speech and countenance, without levity in expression, and airiness of gesture; and that it be the sincere milk of the word that is given forth, and that with all integrity and uprightness of soul: or else this refers to the life and conversation of the teacher, as answering to his doctrine, and going along with it; and the sense is, in, or with doctrine, along with the doctrine preached, let the conversation be pure and incorrupt, free from the pollutions of the world, and from any governing vice; and let it be attended with gravity in word, gesture, look, and dress; and with all sincerity, faithfulness, and simplicity, in all our dealings, either with the saints, or with the men of the world. ~John Gill

3] Showing uncorruptness.

Showing uncorruptness - The word here used does not occur elsewhere in the New Testament. It means, here, the same as purity - that which is not erroneous, and which does not tend to corrupt or vitiate the morals of others, or to endanger their salvation. Everything in his teaching was to be such as to make men purer and better. ~Barnes Notes

4] Gravity.

Gravity - See this word explained in the notes at 1 Timothy 2:2, where it is rendered “honesty;” compare the notes at 1 Timothy 3:4, where it is rendered “gravity.” It does not elsewhere occur; see the use of the adjective, however, in Philippians 4:8; 1 Timothy 3:8, 1 Timothy 3:11; Titus 2:9. The word properly means “venerableness;” then, whatever will insure respect, in character, opinions, deportment. The sense here is, that the manner in which a preacher delivers his message, should be such as to command respect. He should evince good sense, undoubted piety, an acquaintance with his subject, simplicity, seriousness, and earnestness, in his manner. ~Barnes Notes

Quoted verses
1 Timothy 2:2 [see Lesson]
For kings, and for all that are in authority; that we may lead a quiet and peaceable life in all godliness and honesty.

1 Timothy 3:4 [see Lesson]
One that ruleth well his own house, having his children in subjection with all gravity;

1 Timothy 3:8 [see Lesson]
Likewise must the deacons be grave, not doubletongued, not given to much wine, not greedy of filthy lucre;

1 Timothy 3:11 [see Lesson]
Even so must their wives be grave, not slanderers, sober, faithful in all things.

Titus 2:9 [see Lesson]
Exhort servants to be obedient unto their own masters, and to please them well in all things; not answering again.

5] Sincerity.

Sincerity - See this word (ἀφθαρσία aphtharsia) explained in the notes at Ephesians 6:24. It is rendered immortality in Romans 2:7; 2 Timothy 1:10; incorruption, in 1 Corinthians 15:42, 1 Corinthians15:50, 1 Corinthians 15:53-54; and sincerity, Ephesians 6:24, and in the place before us. It does not elsewhere occur in the New Testament. It means incorruption, incapacity of decay; and, therefore, would be here synonymous with purity. ~Barnes Notes

Quoted verses:
Ephesians 6:24
Grace be with all them that love our Lord Jesus Christ in sincerity. Amen.

The commentary on this verse
 

In sincerity - Margin, “with incorruption.” With a pure heart; without dissembling; without hypocrisy. There could not be a more appropriate close of the Epistle than such a wish; there will be nothing more needful for us when we come to the close of life than the consciousness that we love the Lord Jesus Christ in sincerity. ~Barnes Notes

Romans 2:7
To them who by patient continuance in well doing seek for glory and honour and immortality, eternal life:

2 Timothy 1:10 [see Lesson]
But is now made manifest by the appearing of our Saviour Jesus Christ, who hath abolished death, and hath brought life and immortality to light through the gospel:

1 Corinthians 15:42
So also is the resurrection of the dead. It is sown in corruption; it is raised in incorruption:

1 Corinthians 15:50
Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; neither doth corruption inherit incorruption.

1 Corinthians 15:53-54
53 For this corruptible must put on incorruption, and this mortal must put on immortality.
54 So when this corruptible shall have put on incorruption, and this mortal shall have put on immortality, then shall be brought to pass the saying that is written, Death is swallowed up in victory.

So, be like Titus:
1] Do good works and be an example of good works
2] Have and believe sound doctrine. Mix nothing with the truth.
3] Be incorrupt. Enter into nothing that would endanger salvation.
4] Conduct yourself with seriousness, simplicity and earnestness in all spiritual elements. Do not be double-tongued and do not be double-minded.
5] Show no hypocrisy. Have a pure heart. Love the Lord, Jesus Christ.

These are the lessons of verse 7.