Rebbi says: We would have to acknowledge the greatness of Moses only if we assumed that the Holy One Blessed be He retracted His directive (19:21), (which is not the case). Rather, the Holy One Blessed be He said to Moses: I will call you from the top of the mountain and you will ascend, viz. (Ibid. 20) "And the L–rd called Moses to the top of the mountain, and Moses ascended."
Where God Instructs Moses to Go Down and Warn the People Not to
Mekhilta Tractate Bachodesh 2:23