Musar zu Bereschit 45:6

On the verse "There was famine in the land" (12,10), Nachmanides writes as follows: Abraham descended to Egypt on account of the famine, in order to spend some time there to keep alive during the drought, and the Egyptians oppressed him by robbing him of his wife. G–d took revenge on them by striking them with great afflictions and G–d led Abraham out from there with livestock, silver and gold. Pharaoh even ordered his men to make sure that Abraham would depart. Abraham's experience was repeated when Jacob and family descended to Egypt to escape the famine in Canaan, when they were eventually oppressed and the Egyptians separated them from their wives. The Israelites were eventually liberated but only after the Egyptians had been smitten with many plagues. Everything that their patriarch Abraham experienced, his descendants experienced on a national scale. The whole matter is explained by Rabbi Pinchas in the name of Rabbi Oshiyah in Bereshit Rabbah 40,6 who has G–d tell Abraham that he should pave the way for his descendants, and that as a result you find that Abraham's experiences foreshadowed those of his descendants. Example: Abraham experienced famine and moved to Egypt; Joseph told his father Israel that there would be five more years of famine (Genesis 45,6).