Specifically, we're looking at section 47, which tackles the tricky subject of God's promises to both Ishmael and Isaac.

The passage centers around Genesis 17:20, where God says, "And regarding Ishmael, I have heard you; behold, I have blessed him. I will make him fruitful, and I will multiply him exceedingly; twelve princes shall he beget, and I will make him a great nation." Seems pretty straightforward, right? But then comes verse 21: "But My covenant I will keep with Isaac, whom Sarah shall bear you at this designated time next year."

So, who gets what blessing? That's where the rabbinic interpretations come in, offering multiple readings.

Rabbi Yoḥanan, quoting Rabbi Yehoshua ben Ḥanina, suggests a surprising idea: the blessings for Ishmael in verse 20 are actually derived from the blessings intended for Isaac! In other words, "The son of the maidservant may be derived from the son of the mistress." It’s as if God is saying, "I've already planned these blessings for Isaac, and now I'm extending a version of them to Ishmael."

But wait, there's more! Rabbi Abba bar Kahana, citing Rabbi Beiri, flips the script. He suggests the opposite: the blessings in verse 20 primarily refer to Ishmael, but – and this is key – they apply even more so to Isaac! "Here, the son of the mistress may be derived from the son of the maidservant." Isaac, as the son of Sarah, Abraham's wife, receives an even greater blessing. The passage emphasizes, "But My covenant I will keep with Isaac."

What are we to make of these contrasting interpretations? Are the blessings for Ishmael and Isaac connected? Are they independent?

Rabbi Yitzḥak adds another layer. He contrasts Ishmael's descendants, who will produce twelve nesi’im (princes), with the tribes of Israel, the matot. He draws a parallel: "All these are the tribes of Israel, twelve" (Genesis 49:28) – these are the descendants of the mistress. Ishmael would produce only those twelve nesi’im, just as it says: “Clouds [nesi’im], wind, but no rain" (Proverbs 25:14). The implication? Ishmael's leadership will be fleeting, like clouds that promise rain but deliver nothing. In contrast, the tribes of Israel are matot, enduring, "just as it says: 'The oaths to the tribes [matot], an enduring word'" (Habakkuk 3:9).

Finally, Rabbi Huna, in the name of Rabbi Idi, delves into the timing of Isaac's birth. The verse states that Sarah will bear Isaac "at this designated time [lamo’ed] next year." Rabbi Huna points out that the year in question must have been a leap year. Why? Because the phrase "designated time" (mo’ed) alludes to a festival. To allow for a full-term pregnancy between festivals, they reason, that year needed an extra month—a leap year! This kind of intricate textual interpretation is common in rabbinic literature.

What does it all mean? This passage from Bereshit Rabbah isn't just a simple explanation of a biblical verse. It's a window into the complex and nuanced way that the rabbis grappled with questions of lineage, promise, and divine favor. It invites us to consider the relationship between Ishmael and Isaac, and the enduring nature of God's covenant. It highlights the importance of careful reading and interpretation in understanding sacred texts. And it reminds us that even seemingly contradictory interpretations can offer valuable insights.