The Talmud (Menachot.29b) records a story about how Moses could not understand laws expounded 1700 years later in his name:
"Rav Yehuda says that Rav says: When Moses ascended on High, he found the Holy One, Blessed be He, sitting and tying crowns on the letters [of the Torah]. … [God] said to him: There is a man who is destined to be born after several generations, and Akiva ben Yosef is his name. He is destined to derive from each and every thorn [of these crowns] mounds and mounds of laws. It is for his sake that the crowns must be added to the letters of the Torah.
Moses said before God: Master of the Universe, show him to me. God said to him: Return behind you. Moses went and sat at the end of the eighth row in Rabbi Akiva’s study hall and did not understand what they were saying. Moses’ strength waned. [He thought his Torah knowledge was deficient]… [Rabbi Akiva’s] students said: My teacher, from where do you derive this? Rabbi Akiva said to them: It is a law transmitted to Moses from Sinai. When Moses heard this, his mind was put at ease."
Why was Moses uncomfortable at first, then his mind was "put at ease" when he heard that?
(1) Because he realized he must have known it all along, but had forgotten it? (If so, what is the point of the story? That we all get old? Suggested in Parshat Vayelech, Deut 31:1-2.)
(2) Because he was happy to see that what he started would continue and evolve, even past his own ability to understand? (Perhaps Moses thought at first that Akiva was making things up, which made him uneasy, then realized Akiva was deriving it from what Moses himself taught, at which point he relaxed?)