Thou wilt perform the {u} truth to Jacob, and the mercy to Abraham, which thou hast sworn unto our fathers from the days of old.

(u) The Church is assured that God will perform the truth of his merciful promise, which he had made long ago to Abraham, and to all that would apprehend the promise by faith.

Jamieson-Fausset-Brown Bible Commentary

20. perform the truth-the faithful promise.

to Jacob . Abraham-Thou shalt make good to their posterity the promise made to the patriarchs. God's promises are called "mercy," because they flow slowly from grace; "truth," because they will be surely performed (Lu 1:72, 73; 1Th 5:24).

sworn unto our fathers-(Ps 105:9, 10). The promise to Abraham is in Ge 12:2; to Isaac, in Ge 26:24; to Jacob, in Ge 28:13. This unchangeable promise implied an engagement that the seed of the patriarchs should never perish, and should be restored to their inheritance as often as they turned wholly to God (De 30:1, 2).

Matthew Henry's Concise Commentary

7:14-20 When God is about to deliver his people, he stirs up their friends to pray for them. Apply spiritually the prophet's prayer to Christ, to take care of his church, as the great Shepherd of the sheep, and to go before them, while they are here in this world as in a wood, in this world but not of it. God promises in answer to this prayer, he will do that for them which shall be repeating the miracles of former ages. As their sin brought them into bondage, so God's pardoning their sin brought them out. All who find pardoning mercy, cannot but wonder at that mercy; we have reason to stand amazed, if we know what it is. When the Lord takes away the guilt of sin, that it may not condemn us, he will break the power of sin, that it may not have dominion over us. If left to ourselves, our sins will be too hard for us; but God's grace shall be sufficient to subdue them, so that they shall not rule us, and then they shall not ruin us. When God forgives sin, he takes care that it never shall be remembered any more against the sinner. He casts their sins into the sea; not near the shore-side, where they may appear again, but into the depth of the sea, never to rise again. All their sins shall be cast there, for when God forgives sin, he forgives all. He will perfect that which concerns us, and with this good work will do all for us which our case requires, and which he has promised. These engagements relate to Christ, and the success of the gospel to the end of time, the future restoration of Israel, and the final prevailing of true religion in all lands. The Lord will perform his truth and mercy, not one jot or tittle of it shall fall to the ground: faithful is He that has promised, who also will do it. Let us remember that the Lord has given the security of his covenant, for strong consolation to all who flee for refuge to lay hold on the hope set before them in Christ Jesus.