Menachot 29b
R. Y’hudah said in the name of Rav: When Moses went to heaven he found God sitting and affixing crowns to the letters [of the Torah]. Moses said: “Master of the Universe, who detains your hand?" [I.e., why do you take so long to add these crowns to the letters?] God said to him: "A man will come to be at the end of many generations, and Akiva ben Yosef is his name. He will interpret on each and every jot and tittle mounds of laws." He said to him: "Master of the Universe: Show him to me." God said to him: "Turn around." He went and sat at the end of the eighth row, but he did not know what they were saying. He was ill at ease. When he arrived to one point, his students said to him: “Teacher, how do you know it is so?” He replied: “It is halacha given to Moses at Mount Sinai.” And he was comforted.