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. We will begin with the general and move to the specific. First to the Matthew Henry Main which covers verses 9-15. We will pick it up where it begins speaking to verse 15:

IV. The apostle concludes with salutations and benedictions, Titus 3:15. Though perhaps not personally known (some of them at least), yet all by Paul testify their love and good wishes to Titus, owning him thereby in his work, and stimulating him to go on therein. Great comfort and encouragement it is to have the heart and prayers of other Christians with and for us. Greet those that love us in the faith, or for the faith, who are our loving fellow-Christians. Holiness, or the image of God in any, is the great endearing thing that gives strength to all other bonds, and is itself the best. Grace be with you all. Amen. This is the closing benediction, not to Titus alone, but to all the faithful with him, which shows that though the epistle bears the single name of Titus in the inscription, yet it was for the use of the churches there, and they were in the eye, and upon the heart, of the apostle, in the writing of it. “Grace be with you all, the love and favour of God, with the fruits and effects thereof, according to need, spiritual ones especially, 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, his desire of their good, and a means of obtaining for them, and bringing down upon them, the thing requested. Observe, Grace is the chief thing to be wished and begged for, with respect to ourselves or others; it is, summarily, all good. Amen shuts up the prayer, expressing desire and hope, that so it may, and so it shall be. ~Matthew Henry Main

Note: For a salutation, there is much here. This is the way of Paul. He knew his language and he knew how to take us deep in just a few words. Notice:

1] He sends salutations of love and good wishes to Titus from all those with him, even if some of them did not know Titus or anyone with him.
2] He stimulates and encourages Titus forward.
3] He shows [God shows] us that there is comfort and encouragement to know that we have the love and prayers of other Christians.
4] He encourages Titus to greet those in Crete that love Paul, the brethren and the Work of God.
5] It is our individual and collective holiness that gives strength to every one else in the Body of Christ. This lends additional meaning to 1 Peter 1:16 which says, "Because it is written, Be ye holy; for I am holy. It also sheds light on Amos 3:3 which says, "Can two walk together, except they be agreed? Only holy people can walk together in the Body of Christ.
6] The prayer is given to Titus and those with him in Crete, Grace be with you all. Amen.
7] Though this is a letter to Titus, it is for all the churches in Crete. And it is a letter to all the churches of God and all the forward-moving (holy) firstfruits in them.
8] Paul carries the brethren with him in his heart. This is what we are supposed to be doing. We are to carry the brethren in our hearts. This goes far beyond just praying for them.
9] Paul loves the brethren so much that he prays for them grace [pardon of God], the love and favor of God, as well as all the fruits and effects of the salvation process according to the will of God. We are to have the same prayers, not only for the firstfruits but all those around them; their loved ones and friends.
10] Paul [and God] desire that our love and concern for the brethren grows more and more as we mature in the salvation process.
11] It is Paul's wish and prayer to show his affection to all the brethren. His desire is their good and that God provide for them according to their needs and desires.
12] Grace [the pardon of God that allows our entrance into the salvation process and the calling to be in that process] is the chief thing to be wished and begged for, not only for us, individually, but for all the brethren. We are to pray for the good of all brethren. Paul put the, "Amen" to this prayer, expressing his desire and hope that it be so. We follow Paul as he follows Christ and this last verse of Chapter is all about Christ.

Do not let anyone try to tell you this is just some salutation verse to end a letter to Titus.

Now to the Matthew Henry Concise which discusses 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

Now to the Biblical Illustrator that will speak to some of those 12 points I gave you from the Matthew Henry Main.

Greet them that love us in the faith

Christian love

Hence note that religion bindeth man to man in the straightest bond; for

1. The Spirit is the tier [highest level-most important] of it; and hence is it called the unity of the Spirit in the bond of peace; and indeed it must be a wonderful bond that can reconcile such deadly enemies as men are before they come into the kingdom of Christ (Isaiah 11:6).
2. God’s image, wheresoever it is, is exceeding beautiful, and a great binder, especially where renewed and repaired [in our hearts and minds]; which being once espied [seen], let the outward condition be what it can be, a religious heart seeth sufficient matter of love, and will knit the soul unto the soul of such a one.
3. It [Christian love] addeth strength and firmness to all other bonds of nature, affinity, etc., and maketh them more natural. What a true friend was Jonathan to David! Because he saw that God was with him his soul clave unto him; though the kingdom was to be rent from him for it, yet could he not rend his heart from David. If Joseph had not had more than nature, he could not but have revenged such infinite wrongs upon his brethren; whereas the grace of his heart made him say, “It was not you, my brethren, but God sent me before you.” Consider also of the example beyond all imitation of our Lord Jesus Christ, who gave Himself to the death for us when we were yet His enemies.

Quoted verse:
Isaiah 11:6
The wolf also shall dwell with the lamb, and the leopard shall lie down with the kid; and the calf and the young lion and the fatling together; and a little child shall lead them.

Use [Christian love; manifest it]
1. Whence we are taught most familiarly to embrace them that love us in the faith, and to make most account of their love. Many love in the face (friendships), many in the flesh (physically), many in nature (the material world), only the love of Christians is a fruit of faith, a work of the Spirit, and therefore a surer bond than they all. Well knew the apostle that none was in comparison worth having but this; he calleth for no other, he careth for no other, he mentioneth no other.

2. Such as set into any society with others, if he would have it comfortable unto him, let him strengthen all other natural or civil bonds by this bond of religion; let him labour to begin his love in the faith, or, if he have begun elsewhere already, let him reform the same hereby if he look for any sound comfort in his estate; for this is the cause that men often have so little return of love from their wives, so little obedience from their children, so little duty from their servants, so slender respect from their equals, because they begin their love and duties at a wrong end, and have for other respects affected those with whom they live, but the least, if at all, for grace and religion, which of all is the soundest, most profitable, and most comfortable. ~Biblical Illustrator with minor editing by me

Shake hands
Shake hands with somebody as you go out of church. The more of it the better, if it is expressive of real interest and feeling. There may be a great deal of the spirit of the gospel put into a hearty shake of the hand. Think of Paul’s four times repeated request—“Greet one another”—after the custom then in common use, and one which is expressive of even warmer feeling than our common one of handshaking. Why not give your neighbours the benefit of the warm Christian feeling that fills you to your finger tips, and receive the like from them in return? You will both be benefited by it; and the stranger will go away feeling that the Church is not, after all, so cold as he had thought it to be. ~Biblical Illustrator

Christian love
A lady and her little daughter, passing out of church, the child bade goodbye to a poorly dressed little girl. “How did you know her?” inquired the mother. “Why, you see, mamma, she came into our Sabbath School alone, and I made a place for her on my seat, and I smiled and she smiled, and then we were acquainted.” ~Biblical Illustrator

Now to the specific commentaries.

The verse breaks out in three parts:

1] All that are with me salute thee.
2] Greet them that love us in the faith.
3] Grace be with you all. Amen.

1] All that are with me salute thee.

All that are with me salute thee - All the apostles, fellow labourers, and the ministers of the Gospel that were with him; and all the members of the church where he was, sent their Christian salutation to Titus; he being a person greatly esteemed, and whose praise was in all the churches: ~John Gill

2] Greet them that love us in the faith.

Greet them that love us in the faith - not merely as men, as their countrymen, as related to them in the flesh; or on account of any external things, but as believers; because of the doctrine of faith, professed and preached; and because of the grace of faith obtained and possessed; or who love us faithfully, sincerely, and uprightly, from their hearts, and not in word and tongue only. ~John Gill

Greet them that love us in the faith - “Salute them that love us in the faith.” All at Crete had not this love rooted in faith, the true bond of fellowship. A salutation peculiar to this Epistle, such as no forger would have used. ~Jamieson, Fausset, Brown

3] Grace be with you all. Amen.

Grace be with you all, Amen - which is the common concluding salutation in all Paul's epistles. This shows that this epistle was not designed for Titus only, but for the saints at Crete. ~John Gill

Grace be with you all, Amen - Greek, “The grace,” namely, of God. ~Jamieson, Fausset, Brown

Remember those twelve points I gave you, for these are the lessons of verse 15.

1] He sends salutations of love and good wishes to Titus from all those with him, even if some of them did not know Titus or anyone with him.
2] He stimulates and encourages Titus forward.
3] He shows [God shows] us that there is comfort and encouragement to know that we have the love and prayers of other Christians.
4] He encourages Titus to greet those in Crete that love Paul, the brethren and the Work of God.
5] It is our individual and collective holiness that gives strength to every one else in the Body of Christ. This lends additional meaning to 1 Peter 1:16 which says, "Because it is written, Be ye holy; for I am holy. It also sheds light on Amos 3:3 which says, "Can two walk together, except they be agreed? Only holy people can walk together in the Body of Christ.
6] The prayer is given to Titus and those with him in Crete, Grace be with you all. Amen.
7] Though this is a letter to Titus, it is for all the churches in Crete. And it is a letter to all the churches of God and all the forward-moving (holy) firstfruits in them.
8] Paul carries the brethren with him in his heart. This is what we are supposed to be doing. We are to carry the brethren in our hearts. This goes far beyond just praying for them.
9] Paul loves the brethren so much that he prays for them grace [pardon of God], the love and favor of God, as well as all the fruits and effects of the salvation process according to the will of God. We are to have the same prayers, not only for the firstfruits but all those around them; their loved ones and friends.
10] Paul [and God] desire that our love and concern for the brethren grows more and more as we mature in the salvation process.
11] It is Paul's wish and prayer to show his affection to all the brethren. His desire is their good and that God provide for them according to their needs and desires.
12] Grace [the pardon of God that allows our entrance into the salvation process and the calling to be in that process] is the chief thing to be wished and begged for, not only for us, individually, but for all the brethren. We are to pray for the good of all brethren. Paul put the, "Amen" to this prayer, expressing his desire and hope that it be so. We follow Paul as he follows Christ and this last verse of Chapter is all about Christ.