Thanks for your answers. Not surprisingly, Stephen differs from the Jewish commentators/tradition. It’s interesting that you have a NT scriptural source for something that is not explicit in the Torah. (Interesting is a subjective word, but it is data nonetheless.)
It’s interesting that you have a NT scriptural source for something that is not explicit in the Torah
Evidently the NT authors credited some strand of Jewish oral tradition.
Matthew Henry's commentary says:
"[These ages] are traditional. There are that say that Moses was forty years in Pharaoh's palace, forty years in Midian, and forty years in the wilderness" (Tauchum, in Exodus it.). "Moses was forty years in Pharaoh's court, and forty years in Midian, and forty years he served Israel" (Beresh. Rabb. )
I am not familiar with these sources ("Tauchum, in Exodus it." and "Beresh. Rabb.") --- are they rabbinical, possibly?