G-d promises Abraham that his descendants will “as numerous as the sands of the sea, and the stars of the heaven.”
But when Moses predicts the future of the Jewish people, he does not say that we will be as numerous as the sands of the sea. Instead, he tells us, three times, only that we will be “as numerous as the stars in the sky.”
Why? How did we lose the much larger (at least to the naked eye) quantity predicted to Abraham? What changed?
The answer is that nothing changed: sometimes we forget that Abraham had many descendants besides Isaac. He had Ishmael with Hagar and with his second wife, Keturah, he fathered six more: Zimram, Jokshan, Medan, Midian, Ishbak, and Shuah. These he sent away toward the East, where they became nations in their own right. It was those descendants who became numerically enormous, populating the world. They became as numerous as the sands of the sea, which is to say, countless.
But the Jews, under Isaac, were never quantitatively large. Our numbers have never formed the majority population anywhere in the world save for within Israel.
The word used for “numerous” in the Torah (“rav”) also can be understood qualitatively, as in “great” or “important.” (See Gen 6:5) Indeed, it is the same word in Hebrew as “Rabbi,” denoting someone of influence and import, a teacher.
When Moses tells us that the Jewish people will be “as great as the stars in the sky,” he is making an aspirational statement: like stars, we are supposed to be lights unto the world. We are meant to achieve and represents spiritual heights, to always be a directional guide to mankind. Moses’ prediction is thus not a descriptor, but a prescriptor: it is our job to aspire to be holy, to become guiding lights, to show how human animals can become holy.
Thus G-d fulfills Avraham’s blessing: his descendants become numerous as well as influential – but not necessarily through the same sons! And when Moses says that the Jewish people are not the most populous or large of nations but also compares us to the stars, he is making the point that influence and power are often unyoked from each other. Our task is to ignore the power of numbers: we are instead to aspire to be a holy nation.