Moses Learns and Forgets the Torah Until God Gives It as a Gift

Midrash Tanchuma Buber, Ki Tisa 12:1

[(Exodus 31:18:) "And when He had finished speaking with him, He gave unto Moses."] Rabbi Abbahu said: All forty days that Moses spent on high, he would learn Torah and forget it. Moses said to Him: "Master of the Universe, here I have forty days, and I do not know a single thing!" What did the Holy One, blessed be He, do? When he had completed forty days, He gave him the Torah as a gift. "And He gave unto Moses."

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