{3} And the Lord make you to increase and abound in love one toward another, and toward all men, even as we do toward you:

(3) Another part of the epistle, in which he speaks of the duties of a Christian life. And he shows that the perfection of a Christian life consists in two things, that is, in charity toward all men, and inward purity of the heart. And the accomplishment of these things is nonetheless deferred to the next coming of Christ, who will then perfect his work by the same grace with which he began it in us.

People's New Testament

3:12 The Lord make you to increase and abound in love. Whether he may come or not, his prayer is for their increase in love, the greatest of all graces.

Jamieson-Fausset-Brown Bible Commentary

12. The "you" in the Greek is emphatically put first; "But" (so the Greek for "and") what concerns "YOU," whether we come or not, "may the Lord make you to increase and abound in love," &c. The Greek for "increase" has a more positive force; that for "abound" a more comparative force, "make you full (supplying 'that which is lacking,' 1Th 3:10) and even abound." "The Lord" may here be the Holy Spirit; so the Three Persons of the Trinity will be appealed to (compare 1Th 3:13), as in 2Th 3:5. So the Holy Ghost is called "the Lord" (2Co 3:17). "Love" is the fruit of the Spirit (Ga 5:22), and His office is "to stablish in holiness" (1Th 3:13; 1Pe 1:2).

Matthew Henry's Concise Commentary

3:11-13 Prayer is religious worship, and all religious worship is due unto God only. Prayer is to be offered to God as our Father. Prayer is not only to be offered in the name of Christ, but offered up to Christ himself, as our Lord and our Saviour. Let us acknowledge God in all our ways, and he will direct our paths. Mutual love is required of all Christians. And love is of God, and is fulfilling the gospel as well as the law. We need the Spirit's influences in order to our growth in grace; and the way to obtain them, is prayer. Holiness is required of all who would go to heaven; and we must act so that we do not contradict the profession we make of holiness. The Lord Jesus will certainly come in his glory; his saints will come with him. Then the excellence as well as the necessity of holiness will appear; and without this no hearts shall be established at that day, nor shall any avoid condemnation.