The oath - This oath is recorded in Genesis 22:16-17. It was an oath in which God swore by himself (because he could swear by no greater, Hebrews 6:13-14) that he would surely bless Abraham and his posterity. That promise was now to be entirely fulfilled by the coming of the Messiah.
Related Commentaries of Luke 1:73
Luke 1:73
73 The oath which he sware to our father Abraham,