Midrash su Genesi 39:5

And thus do you find, that wherever the righteous go, blessing comes in their wake. Israel went down to Gerar — blessing came to Gerar, viz. (Bereshith 26:12) "And Israel sowed in that land, etc." Jacob went down to Lavan — blessing came down in his wake, viz. (Ibid. 30:27) "I have found through divination that the L-rd has blessed me for your sake." Joseph went down to Potifera — blessing came in his wake, viz. (Ibid. 39:5) "and the L-rd blessed the house of the Egyptian for Joseph's sake." Jacob went down to Pharaoh — blessing came down for his sake, viz. (Ibid. 47:10) "And Jacob blessed Pharaoh." In what way did he bless him? In that years of famine were withheld from him. And after the death of Jacob they returned, as it is written (Ibid. 50:21) "And now, do not fear, I (Joseph) will feed you and your little ones," and (Ibid. 45;11) "And I will feed you there." Just as "feeding" there was in the (projected) years of famine, so, the "feeding" here (50:21) was in the years of famine, (the famine having returned with Jacob's death). These are the words of R. Yossi.

AND HE LEFT ALL THAT HE HAD IN JOSEPH'S HAND; AND, HAVING HIM, HE KNEW NOT AUGHT SAVE THE BREAD THAT HE DID EAT (XXXIX, 6). This is a euphemism. [It refers to his wife.]