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 (Luk 1:72, Luk 1:73; 1Th 5:24).
sworn unto our fathers - (Psa 105:9, Psa 105:10). The promise to Abraham is in Gen 12:2; to Isaac, in Gen 26:24; to Jacob, in Gen 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 (Deu 30:1, Deu 30:2).