This section has 4 verses.
 
Titus 3:12-15
12 When I shall send Artemas unto thee, or Tychicus [TIK-uh-kus], be diligent to come unto me to Nicopolis [nih-KOP-uh-lis]: for I have determined there to winter.
13 Bring Zenas the lawyer and Apollos on their journey diligently, that nothing be wanting unto them.
14 And let ours also learn to maintain good works for necessary uses, that they be not unfruitful.
15 All that are with me salute thee. Greet them that love us in the faith. Grace be with you all. Amen.
 
We will begin with the Barclay commentary.

FINAL GREETINGS

First, the paraphrase of verses 12-15:

When I send Artemas or Tychicus [TIK-uh-kus] to you, do your best to come to me at Nicopolis [nih-KOP-uh-lis], for I have decided to spend the winter there.
Do your best to help Zenas the lawyer and Apollos on their way. See to it that nothing is lacking to them. And let our people too learn to practice fine deeds, that they may be able to supply all necessary needs, and that they may not live useless lives.
All who are with me send you their greetings. Greet those who love us in the faith.
Grace be with you all. Amen.

AS usual, Paul ends his letter with personal messages and greetings. Of Artemas, we know nothing at all. Tychicus [TIK-uh-kus] was one of Paul’s most trusted messengers. He was the bearer of the letters to the Colossian and the Ephesian churches (Colossians 4:7; Ephesians 6:21). Nicopolis [nih-KOP-uh-lis] was in Epirus [ih-PI-ruhs] and was the best centre for work in the Roman province of Dalmatia. It is interesting to remember that it was there that Epictetus [eh'pih-KYUR-uhs], the great Stoic philosopher, later had his school.

Quoted verses:
Colossians 4:7
All my state shall Tychicus declare unto you, who is a beloved brother, and a faithful minister and fellowservant in the Lord:

Ephesians 6:21
But that ye also may know my affairs, and how I do, Tychicus, a beloved brother and faithful minister in the Lord, shall make known to you all things:

Apollos was the well-known teacher (Acts 18:24). Of Zenas [ZEE-nuhs], we know nothing at all. He is here called a nomikos. That could mean one of two things. Nomikos is the regular word for a scribe, and Zenas may have been a converted Jewish Rabbi. It is also the normal Greek for a lawyer; and, if that is its meaning, Zenas has the distinction of being the only lawyer mentioned in the New Testament.

Quoted verse:
Acts 18:24
And a certain Jew named Apollos, born at Alexandria, an eloquent man, and mighty in the scriptures, came to Ephesus.

Paul’s last piece of advice is that the Christian people should practice good deeds, so that they themselves should be independent and also able to help others who are in need. Christian workers work not only to have enough for themselves but also to have something to give away.

Next come the final greetings; and then, as in every letter,

Paul’s last word is grace. ~Barclay Commentary
 

Now to the other commentaries.  As usual, we will begin with the general and go to the specific.  First to the Matthew Henry.  We are going to pick it up where we left off last time.  It is finishing up with verse 13 and then goes into verse 14.

2. The other personal charge to Titus is that he would bring two of his friends on their journey diligently, and see them furnished, so that nothing should be wanting to them. This was to be done, not as a piece of common civility only, but of Christian piety, out of respect both to them and the work they were sent about, which probably was to preach the gospel, or to be in some way serviceable to the churches. Zenas is styled the lawyer, whether in reference to the Roman or the Mosaic law, as having some time been his profession, is doubtful. Apollos was an eminent and faithful minister. Accompanying such persons part of their way, and accommodating them for their work and journeys, was a pious and needful service; and to further this, and lay in for it, what the apostle had before exhorted Titus to teach (Titus 3:8) he repeats here: Let ours also learn to maintain good works for necessary uses, that they be not unfruitful, Titus 3:14. Let Christians, those who have believed in God, learn to maintain good works, especially such as these, supporting ministers in their work of preaching and spreading the gospel, hereby becoming fellow-helpers to the truth, 3 John 1:5-8. That they be not unfruitful. Christianity is not a fruitless profession; the professors of it must be filled with the fruits of righteousness, which are by Jesus Christ, to the glory and praise of God. It is not enough that they be harmless, but they must be profitable, doing good, as well as eschewing evil. - “Let ours set up and maintain some honest labour and employment, to provide for themselves and their families, that they be not unprofitable burdens on the earth;” so some understand it. Let them not think that Christianity gives them a writ of ease; no, it lays an obligation upon them to seek some honest work and calling, and therein to abide with God. This is of good report, will credit religion and be good to mankind; they will not be unprofitable members of the body, not burdensome and chargeable to others, but enabled to be helpful to those in want. To maintain good works for necessary uses; not living like drones on the labours of others, but themselves fruitful to the common benefit. ~Matthew Henry Main

Quoted verses:
Titus 3:8 [see Lesson]
This is a faithful saying, and these things I will that thou affirm constantly, that they which have believed in God might be careful to maintain good works. These things are good and profitable unto men. 

3 John 1:5-8
5 Beloved, thou doest faithfully whatsoever thou doest to the brethren, and to strangers;
6 Which have borne witness of thy charity before the church: whom if thou bring forward on their journey after a godly sort, thou shalt do well:
7 Because that for his name's sake they went forth, taking nothing of the Gentiles.
8 We therefore ought to receive such, that we might be fellowhelpers to the truth.

Now the Matthew Henry concise. It covers verses 12-15.

Christianity is not a fruitless profession; and its professors must be filled with the fruits of righteousness, which are by Jesus Christ, to the glory and praise of God. They must be doing good, as well as keeping away from evil. Let “ours” follow some honest labour and employment, to provide for themselves and their families. Christianity obliges all to seek some honest work and calling, and therein to abide with God. The apostle concludes with expressions of kind regard and fervent prayer. Grace be with you all; the love and favour of God, with the fruits and effects thereof, according to need; and the increase and feeling of them more and more in your souls. This is the apostle's wish and prayer, showing his affection to them, and desire for their good, and would be a means of obtaining for them, and bringing down on them, the thing requested. Grace is the chief thing to be wished and prayed for, with respect to ourselves or others; it is “all good.” ~Matthew Henry concise

That they be not unfruitful

Christianity fruitful
The metaphor implieth that as the Church is God’s orchard or garden, and His ministers are His planters and waterers, so the faithful are the trees, even trees of righteousness, the planting of the Lord, and planted by the rivers of waters, that they might bring forth their fruit in due season; and teacheth that true Christianity is not a barren but a fruitful profession, unto which Christians are everywhere called.

Quoted verse in next section of text:
Ezekiel 47:12
And by the river upon the bank thereof, on this side and on that side, shall grow all trees for meat, whose leaf shall not fade, neither shall the fruit thereof be consumed: it shall bring forth new fruit according to his months, because their waters they issued out of the sanctuary: and the fruit thereof shall be for meat, and the leaf thereof for medicine.

In Ezekiel 47:12, we have a notable resemblance of those manifold fruits, which by the power of the gospel should be by believers produced in the Church of the New Testament. The vision was of waters which ran from the Temple, and from under the threshold of the sanctuary. And wheresoever these waters should run, they should cause admirable fruitfulness, in so much as on both sides of the river shall grow all kind of fruitful trees, whose leaves shall not fade, and their fruit shall not fail. These waters are the gospel which issue from under the threshold: that is, from Christ the door, typified by that beautiful gate of the Temple; from the Temple at Jerusalem these waters were with swift current to run not only over Judaea, but all the world in a short space: hence was the Church mightily increased, for though these waters run into the dead sea, wherein (if we believe [man’s] histories) abideth no living thing, yet such a quickening power they carry with them, as even there everything shall live; such as were dead in trespasses and sins are hereby quickened, and become trees of righteousness green and flourishing, yea, and constantly fruitful in all godly conversation [conduct].

Quoted verse in next section of text:
John 15:17
These things I command you, that ye love one another.

And this the same which our Saviour noteth (John 15:17), that His Father is the husbandman, Himself is the Vine, Christians are the branches of that vine, who if they be found, His Father purgeth that they may bring forth more fruit; teaching us hereby that it is the Lord’s scope and aim that Christians should be abundant in fruits beseeming their profession. The Apostle Paul accordingly exhorteth the Philippians to be much in goodness, to abound in love, in knowledge, and in all judgment; yea, to be filled with fruits of righteousness which are by Jesus Christ unto the glory and praise of God. And the same apostle calleth rich men to be rich in good works.

I. The conditions of this fruitfulness.

1. Every Christian must be fruitful; for every fruitless branch is cut down and made fuel for the fire.

2. Every Christian must bring forth good fruit.

3. This fruitfulness must proceed from good causes.

(1) The tree must be good, for men gather not grapes of thistles.

(2) He must have a good root (John 15:4),

Quoted verse:
John 15:4
Abide in me, and I in you. As the branch cannot bear fruit of itself, except it abide in the vine; no more can ye, except ye abide in me.

(3) He must draw thence good sap and juice through the fellowship and communion of Christ’s death and resurrection.

(4) He must have the Spirit of the Son to be a principal agent in the setting and ripening of these fruits.

(5) He must have the love of God within him, constraining him, which will be as the sun helping on these fruits to their perfection.

(6) He must have good ends in his eye, viz., God’s glory and man’s good (Philippians 1:2).

Quoted verse:
Philippians 1:2
Grace be unto you, and peace, from God our Father, and from the Lord Jesus Christ.

4. Every Christian must bring forth much fruit, and not for clusters scarce berries, trees of righteousness are: laden with the fruits of the Spirit; and herein is the Father glorified, that ye bring forth much fruit (John 15:8).

Quoted verse:
John 15:8
Herein is my Father glorified, that ye bear much fruit; so shall ye be my disciples.
 

5. Christians must continue fruitful and grow daily more fruitful (John 15:2).

Quoted verse:
John 15:2
Every branch in me that beareth not fruit he taketh away: and every branch that beareth fruit, he purgeth it, that it may bring forth more fruit. ~Biblical Illustrator

Now to the specific commentaries.

I see this verse in four parts as the Barnes Notes commentary has it.
1] And let ours.
2] Also learn to maintain good works.
3] For necessary uses.
4] That they be not unfruitful.

I am going to take them one at a time this week.  First the Barnes Notes.

And let ours - Our friends; that is, those who were Christians Paul had just directed Titus to aid Zenas and Apollos himself, and he here adds that he wished that others who were Christians would be characterized by good works of all kinds.

To maintain good works - Margin, profess honest trades. The Greek will admit of the interpretation in the margin, or will include that, but there is no reason why the direction should be supposed to have any special reference to an honest mode of livelihood, or why it should be confined to that. It rather means, that they should be distinguished for good works, including benevolent deeds, acts of charity, honest toil, and whatever would enter into the conception of an upright life; see the notes at Titus 3:8.

Quoted verse:
Titus 3:8 [see Lesson]
This is a faithful saying, and these things I will that thou affirm constantly, that they which have believed in God might be careful to maintain good works. These things are good and profitable unto men.

For necessary uses - Such as are required by their duty to their families, and by the demands of charity; see Titus 3:8.

Quoted verse:
Mark 6:3
Is not this the carpenter, the son of Mary, the brother of James, and Joses, and of Juda, and Simon? and are not his sisters here with us? And they were offended at him.

All this is a call to you as firstfruits.  Learn all you can about good works and the invoking of the power of the Holy Spirit.  Maintain and do these works constantly and continually for the sake of the church and to those in need.  Be the fruitful branch and stay connected to Christ [the vine].  These are the lessons of verse 14.