The Torah, and the rabbinic tradition that blossoms from it, is obsessed with this very question. Let's dive into a fascinating passage from Bereshit Rabbah 53, a midrash – a rabbinic interpretation – on the verses in Genesis about Sarah finally conceiving Isaac.

The passage kicks off with a quote from I Kings, Solomon's prayer at the dedication of the Temple: "Lord, God of Israel… who upheld for Your servant David, my father, what You had spoken to him." (I Kings 8:23–24). Bereshit Rabbah sees this as a pattern, a divine precedent. Just as God keeps promises to David, so too did God remember Sarah. “Who upheld for Your servant” – this, the midrash says, refers to Abraham. “What You had spoken to him” – that is, "at the prescribed time, I will return to you.” The promise, spoken long ago, finally comes to fruition. “You spoke with Your mouth, and You fulfilled it with Your hand, on this day” (I Kings 8:24) – and this is linked directly to Genesis 21:1–2: “the Lord remembered Sarah […and Sarah conceived, and bore Abraham a son in his old age, at the appointed time that God had spoken to him].”

The midrash then turns to Psalms 113:9: “He sets the barren woman at home, the mother of children is joyful.” This verse, according to the Rabbis, perfectly encapsulates Sarah's transformation. "He sets the barren woman at home" – that's Sarah, the Sarah who "was barren" (Genesis 11:30). "The mother of children is joyful" – that's Sarah, too, the Sarah who "would nurse children" (Genesis 21:7).

But the midrash doesn’t stop there. The verse in Genesis says, "The Lord remembered Sarah as He had said, [and the Lord did to Sarah as He had spoken]." Why the double language? Why "said" and "spoken"? The Rabbis, masters of close reading, see significance in every word. What He Himself had "said" to her was communicated with saying, while "The Lord did to Sarah as He had spoken" refers to what He had spoken to her by means of an angel. It’s a subtle distinction, highlighting the different ways God communicates promise and fulfillment.

Rabbi Nechemya, however, flips the script. According to him, what He had said to her by means of an angel was with saying, while what He Himself had spoken to her was what He actually did.

Then comes Rabbi Yehuda, who offers yet another layer. "As He had said" – to grant her a son. "As He had spoken" – to bless her with milk. Rabbi Nechemya challenges this, pointing out that Sarah never received tidings about producing milk. This leads to another interpretation: God restored her to the days of her youth.

Rabbi Abahu adds that God imposed fear of her upon all the nations of the world, so they would not torment her and call her the barren woman. Imagine the societal stigma Sarah endured, and how this divine act protected her from further pain.

And then, a truly radical idea from Rabbi Yehuda in the name of Reish Lakish: She did not even have a womb, and the Holy One blessed be He now carved out a womb for her. This is more than just a miraculous pregnancy; it's a complete, transformative creation.

Finally, Rabbi Ada offers a powerful analogy: God is a "keeper of deposits [pikdonot]." Amalek deposited with God bundles of thorns – their animosity towards Israel. God returned those thorns. Sarah, on the other hand, deposited with God mitzvot and good deeds. And God returned to her mitzvot and good deeds – "the Lord remembered Sarah." In other words, she was granted a son who would become a righteous person and perform mitzvot, fulfilling her legacy of good.

So, what does it all mean? This passage from Bereshit Rabbah isn't just about a miracle birth. It’s about the nature of promise and fulfillment, the multifaceted ways God interacts with humanity, and the profound impact of righteous actions. It’s about a transformation so complete that it transcends even the physical limitations of the body. And ultimately, it's a reminder that even in the face of seemingly impossible circumstances, hope, faith, and good deeds can shape our destiny. What "deposits" are we making in the world, and what kind of "remembrance" are we hoping for?