Albert Barnes Commentary Luke 1:73

"The oath which he spake unto Abraham our father," — Luke 1:73 (ASV)

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.