I will teach transgressors thy ways Here he speaks of the gratitude which he would feel should God answer his prayer, and engages to show it by exerting himself in effecting the conversion of others by his example. Those who have been mercifully recovered from their falls will feel inflamed by the common law of charity to extend a helping hand to their brethren; and in general, such as are partakers of the grace of God are constrained by religious principle, and regard for the divine glory, to desire that others should be brought into the participation of it. The sanguine manner in which he expresses his expectation of converting others is not unworthy of our notice. We are too apt to conclude that our attempts at reclaiming the ungodly are vain and ineffectual, and forget that God is able to crown them with success.

Then will I teach transgressors thy ways - As an expression of gratitude, and as the result of his own painful experience. He would show them, from that experience, the evil and the bitterness of sin in itself; he would show them with what dreadful consequences sin must always be followed; he would show them the nature of true repentance; he would show them what was required in order that sin might be forgiven; he would encourage them to come to that God who had forgiven him. So the Saviour charged Peter, from his own bitter experience in having fallen under the power of temptation, to strengthen and encourage those who were struggling with the depravity of their own hearts, and who were in danger of falling: "And when thou art converted, strengthen thy brethren," Luke 22:32.
And sinners shall be converted unto thee - They would see from his case the evil of transgression; they would learn from his example that mercy might be found; they would be persuaded to flee from the wrath to come. The best preparation for success in winning souls to God, and turning them from the error of their ways, is a deep personal experience of the guilt and the danger of sin, and of the great mercy of God in its forgiveness. No man can hope to be successful who has not experienced this in his own soul; no one who has, will labor wholly in vain in such a work.

Then will I teach transgressors - I will show myself to be grateful; I will testify of thy loving-kindness; I will call on transgressors to consider the error of their ways; and shall set before them so forcibly thy justice and mercy, that sinners shall be converted unto thee. With a little change I can adopt the language of Dr. Delaney on this place: "Who can confide in his own strength, when he sees David fall? Who can despair of Divine mercy when he sees him forgiven? Sad triumph of sin over all that is great or excellent in man! Glorious triumph of grace over all that is shameful and dreadful in sin!"

[Then] will I teach transgressors thy (l) ways; and sinners shall be converted unto thee.
(l) He promises to endeavour that others by his example may turn to God.

Then will I teach transgressors thy ways,.... David was a prophet as well as a king; see Acts 2:30; and taught men the fear of the Lord, Psalm 34:11, and instructed them in his ways, as he here promises he would; by which are meant, either the ways which God prescribes and directs men to walk in, as the paths of faith, holiness, and truth, and the ways of his commandments; or which he himself has walked in; meaning not the ways of his providence, which are sometimes past finding out; but the ways of his grace, the steps and methods he has taken in the salvation of men, by forming the scheme of it, by choosing unto it, by making a covenant with his Son, and appointing him to effect it; and particularly his ways and methods in receiving and pardoning backsliders, when returned by repentance to him; and who may be meant by "transgressors" here: and then the sense is, that David, upon his being received and pardoned, would teach others like himself how graciously God had dealt with him; how plenteous he is in mercy; how ready to forgive, and how faithful to his promises; and so encourage them to go to him, and acknowledge their transgressions, and seek pardoning grace at his hands, who does abundantly pardon, and whose ways are not as theirs; see Isaiah 55:7;
and sinners shall be converted unto thee: or "that sinners may be converted unto thee" (p); this being the end of teaching by the word, and the means of the conversion of profane and unregenerate sinners, through the power of divine grace; though rather this seems to be understood of the conversion of God's own people after backslidings, and not of first conversion; see Luke 22:32.
(p) "ut peccatores convertantur", Junius & Tremellius, Gejerus, Michaelis.

Then--Such will be the effect of this gracious work.
ways--of providence and human duty (Psalm 18:21, Psalm 18:30; Psalm 32:8; Luke 22:32).