מדרש על בראשית 41:49

What is written before this verse in Scripture? And all the countries came into Egypt to Joseph to buy corn (ibid. 41:57). They did so because he had devoted himself to accumulating corn, as is said: And Joseph laid up corn … during the seven years of plenty. And the seven years of famine began to come, according as Joseph had said (Gen. 41:49–53).