Luke 1:73

I think that at the coming of our Lord and Saviour Jesus Christ, both Abraham, Isaac, and Jacob, were partakers of His mercy. For it is not to be believed, that they who had before seen His day, and were glad, should afterwards derive no advantage from His coming, since it is written, Having made peace through the blood of his Cross, whether in earth or in heaven. (Coloss. 1:20.)

(Hom. in Ps. 29. et in Ps. 14. App. op.) But let no one, hearing that the Lord had sworn to Abraham, be tempted to swear. For as when the wrath of God is spoken of, it does not signify passion but punishment; so neither dos God swear as man, but His word is in very truth expressed to us in place of an oath, confirming by an unchangeable sentence what He promised.

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.