Acts 7:12

But when Jacob heard that there was corn in Egypt,.... Not then growing, or gathering in there, or that was of that year's produce; for the famine was strong in the land of Egypt, as well as in Canaan; but was what had been laid up, and preserved in the seven years of plenty, by the order and care of Joseph; which by some means or another, Jacob had heard of; see Genesis 42:1 the Jews suggest u, that it was by divine revelation:

he sent out our fathers first; the first time, or the first year of the famine; or he sent them first, he laid his commands on them, or they had not gone; these were the ten sons of Jacob, and brethren of Joseph, who were sent the first time, for Benjamin stayed with his father: see Genesis 42:3.

u Bereshit Rabba, sect. 91. fol. 78. 1, 2.