“To perform the mercy promised to our fathers, and to remember his holy covenant, the oath which he swore to our father Abraham” (Luke 1:72-73): it seems needful to say that God exercises his mercy upon us in memory of our fathers. To disabuse us of any confidence in our own justice, and to make us better understand that we are saved by grace, the holy priest Zechariah prefers to say that God performs his mercy toward our fathers who have pleased him rather than to their ungrateful children, that God saves us by his goodness and not according to our merits, that is, to satisfy his promise rather than to repay our works, which are so evil.
We must believe that the merits of the saints are graces from God. The grace that gives good works to us is given without our meriting it. When one is holy, one has merit. Yet, to be holy, there must first be a promise made from God’s pure goodness. The reward is indeed due to those who do good works; but the grace — which is not merited — precedes those good works and enables them to be done. Children of grace and of the promise, live in this faith: it is the new alliance that God has made with us, “so that no human being might boast in the presence of God,” and so that he “who boasts, [boasts] of the Lord” (1 Cor. 1:29, 31).
According to “the oath which he swore to our father Abraham” — the mystery of these words cannot be better expressed than by the letter to the Hebrews. “When God made a promise to Abraham, since he had no one greater by whom to swear, he swore by himself” (Heb. 6:13). Thus it is written: “By myself I have sworn, says the Lord.” So Abraham, the apostle continues, “having patiently endured, obtained the promise.” For as men “swear by a greater than themselves,” and the oath by which they bring the omnipotence and truth of God into their engagement is “in all their disputes . . . final for confirmation,” so also “when God desired to show more convincingly to the heirs of the promise the unchangeable character of his purpose, he interposed with an oath, so that through two unchangeable things [that is, God’s word and the oath that confirmed it], in which it is impossible that God should prove false, we who have fled for refuge might have strong encouragement to seize the hope set before us” (Heb. 6:16-18).
No commentary need be offered here; all we need do is listen to the words and let them penetrate us. Let us only take care that in attaching ourselves to the promise, we do not presume on it. God has promised the remission of sins to the penitent, but he has not promised unlimited patience to those who endlessly tax it.