Luke 1:72

To perform the mercy promised to our fathers
By "mercy" is meant salvation by Christ, which springs from the mercy of God; the promise of which was an instance of mercy to the Jewish fathers under the Old Testament, and also the performance of it; for they were saved by the grace of our Lord Jesus, even as we: his blood was shed for the remission of sins that were past, and for the redemption of transgressions under the first Testament:

and to remember his holy covenant;
which was made between him, and his Son from all eternity; and was, at various times, dispensed and manifested to the patriarchs, and eminent saints, as Adam, Noah, Abraham This is called an "holy" one; not only because it was made by, and between holy persons, and provided for the holiness of the people of God, both here, and hereafter; but because in the article of redemption and salvation by Christ, which is here more particularly regarded, care was taken to secure the glory of God's holiness and justice, as well as to display his grace and mercy. Now raising up, and sending Jesus a Saviour, showed, that God was mindful of this covenant, and therefore sent redemption to his people.