וְכ֖וּשׁ יָלַ֣ד אֶת־נִמְרֹ֑ד ה֣וּא הֵחֵ֔ל לִֽהְי֥וֹת גִּבֹּ֖ר בָּאָֽרֶץ׃
And Cush begot Nimrod; he began to be a mighty one in the earth.
Siftei Chakhamim
Who told Avraham, “Jump...” Rashi is answering the question: Was not Nimrod [not Amraphel] the king of Shinar?