Theophylact of Ohrid — as excerpted in the Catena Aurea on Luke 1:72-74

“The grace of Christ extends even to those who are dead, because through Him we shall rise again, not only we, but they also who have been dead before us. He performed His mercy also to our forefathers in fulfilling all their hopes and desires. Hence it follows, And to remember his holy covenant, that covenant, namely, wherein he said, Blessing, I will bless thee, and multiplying, I will multiply thee. (Gen. 22:17.) For Abraham was multiplied in all nations, who became his children by adoption, through following the example of his faith. But the fathers also, seeing their children enjoy these blessings, rejoice together with them, just as if they received the mercy in themselves. Hence it follows, The oath which he sware to our father Abraham, that he would grant unto us.”