מדרש אויף בראשית 41:18

And Pharaoh said unto Joseph: “I have dreamed a dream (ibid.). As he was about to relate the dream to him, he decided to test Joseph by altering the dream slightly. He said: “Seven kine went up out of the Nile, fat and well-formed,” whereupon Joseph replied: “That is not so, you saw fat and healthy kine.” “And there were,” he said to him, “seven lean and ill-favored kine.” And Joseph replied: “You did not see this but rather ugly-appearing and thin-fleshed kine.” “And there were seven full and good ears of corn,” he continued. Whereupon Joseph answered: “That too is not so, you saw fat and good ones.” “There were seven shrunken ears of corn,” he added. And Joseph responded: “That is not so, you beheld seven ears of corn, withered thin and blistered by the east wind.” Pharaoh began to wonder about this. He said to him: “You must have been behind me when I had my dream,” as it is said: For inasmuch as God hath shown thee all this, there is none so discreet and wise as thou (ibid. v. 39).

“Pharaoh sent and summoned Joseph, [and they rushed him from the dungeon. He shaved, changed his garments, and came to Pharaoh]” – to accord deference to royalty.²³That is why, although others rushed him, he shaved himself.
“Joseph answered Pharaoh, saying: Not by me. God will respond for Pharaoh’s peace” (Genesis 41:16).
“Joseph answered Pharaoh, saying: Not by me. God [will respond]” – He attributed the greatness to its initiator.
“And, behold, seven cows, fat fleshed and fair of appearance came up from the Nile, and they grazed in the pasture” (Genesis 41:18).
“Seven cows” – Rabbi Yehuda and Rabbi Neḥemya, Rabbi Yehuda said: It should have been fourteen years, as that is what Pharaoh saw.²⁴The seven lean cows and seven blighted stalks should have indicated fourteen years. Rabbi Neḥemya said: They were twenty-eight years, as that is what Pharaoh said to Joseph.²⁵Pharaoh’s very mention of the seven lean cows and blighted stalks to Joseph should have initiated an additional seven years for each. The Rabbis say: It should have been forty-two years, for what Pharaoh saw and said to Joseph, and [for what] Joseph repeated and said to Pharaoh. Rabbi Yosei ben Ḥanina said: The famine lasted two years, as once Jacob our patriarch descended there, the famine ceased. When did it return? In the days of Ezekiel. That is what is written: “I will render the land of Egypt desolation among desolate lands, and its cities will be desolation among ruined cities for forty years” (Ezekiel 29:12).