Genesis 41:27
And the seven thin and ill favoured kine that came up after them are seven years; and the seven empty ears blasted with the east wind shall be seven years of famine. And the seven thin and ill favoured kine that came up after them are seven years; and the seven empty ears blasted with the east wind shall be seven years of famine.
The seven thin and ill-favored cows that came up afterward and the seven empty ears blasted by the east wind mean the same thing, seven years of famine. Those seven years of famine will follow seven years of great plenty in Egypt. During the plenteous years everything will grow in great abundance, with field and garden yielding more plentifully than formerly, more abundantly than ever before, and fruits and grains yielding abundantly.
The years of abundance are given so that preparation can be made for the coming years of famine. The warning requires looking out a discreet and wise man and setting him over the land, with officers over Egypt. In the plenteous years they are to take up the fifth part of the land and gather and keep corn under Pharaoh's hand in the cities for store against the seven years of famine.
The coming famine will be so very grievous that the former plenty will not be known in the land and will scarcely be remembered. God showed Pharaoh in the dream what He is about to do, and the giving of the dream twice in two forms, doubled to Pharaoh, proves the thing is firmly established by God and will shortly, certainly and soon come to pass. God revealed the coming famine to Joseph in a dream seven years beforehand, enabling Egypt to store food for those years. When the famine came, people from other countries, including Jacob's family in Canaan, went to Egypt to buy grain.