This is the prophecy Rebekah receives in the study house of Shem, and it reframes every story that follows. Targum Pseudo-Jonathan on Genesis 25:23 preserves the oracle with one crucial addition.
"Two peoples are in thy womb, and two kingdoms from thy womb shall be separated; and one kingdom shall be stronger than the other, and the elder shall serve the younger" — and then the Targum's expansion — "if the children of the younger will keep the commandments of the Law."
Read that final clause slowly. The Targum has turned a flat prophecy into a conditional one. The elder will serve the younger, yes, but only if the younger's descendants keep Torah. The supremacy of Jacob's line over Esau's is not automatic. It is covenantal. It depends on faithfulness.
This is the Targum's entire theology of Jewish history compressed into one subordinate clause. Israel's destiny is real but conditional. When Israel keeps the Torah, Israel rises. When Israel abandons the Torah, the elder kingdom — Esau, whom the Rabbis identified with Rome and many hostile empires — regains the upper hand. The oracle was not a magic spell. It was a contract.
Rebekah leaves the beit midrash with a prophecy and a warning folded into the same sentence. She is carrying not only two children but two possible futures, and the children she bears will have to choose which future activates.
Every time the Jewish people have suffered under a Roman, Babylonian, Persian, or Hellenistic empire, the midrashic mind has asked the Targum's question. Have we been keeping the Torah? The oracle in the womb is the oldest answer: the conditions of your strength were written before you were born, and they were written in the language of faithfulness.