In our parsha (reading), Hashem tells our forefather, “do not fear, Avram, I will shield you, your reward is very great” [15:1]. And Avram replies in the following verse, “Hashem, what will you give me, and I go childless…” [This was before Avraham and Sarah were renamed by G-d.]
The Maleh HaOmer asks, Why does Avram wait until now to pray for a child? The Torah notes that Sarai was childless much earlier, at the end of Parshas Noach (11:30). What changed?
The Talmud in Shabbos says, “there is no ‘fortune’ for Jews.” But Tosfos points out a contradiction, because our Sages also say that “children, livelihood and food do not depend upon merits, but good fortune,” meaning that it is G-d who makes our efforts succeed in these areas. These two statements contradict each other, so how can they be reconciled?
The answer, says the Maleh HaOmer, is that a great, exceptional merit can change a person’s fortune.
So Avraham knew that fortune said he could not have a child, and therefore did not pray for one. But when HaShem told him “your reward is very great,” this implied that he had great merits, able to change what was decreed for him. And thus he immediately responded by asking and praying for children.
And indeed his prayer was answered favorably, as G-d “took him out,” out of the realms of fortune and what was decreed for him, and told Avraham that his descendants would be as innumerable as the stars (v. 5).
Very few people have the exceptional merits necessary to change fortune—otherwise they would not be exceptional! But we are children of Avraham, Yitzchak, and Yaakov, and we remember them in our prayers because their tremendous merits can stand for each of us when we pray for our own needs.