Why did God tell Jacob to go down into Egypt?
God told Jacob to go down into Egypt because He would there make of him a great nation (Genesis 46:3). It was part of God's sovereign plan, and in Egypt Joseph could provide grain during the famine in Canaan, settling them in Goshen.
Les explains that although the promise had always been associated with staying in the land of promise, in God's sovereign plan He finally tells Jacob in no uncertain terms to go down into Egypt. Genesis 46:3 records God's assurance: “I am God, the God of thy father, fear not to go down into Egypt, for I will there in Egypt make of thee a great nation.” The family was about to starve in Canaan, but there was grain in Egypt, and Joseph, second highest in Egypt, gave them the fruit of the land around the Nile called Goshen. Les notes those twelve sons became the setting for the population explosion leading into Exodus, and God would make them a great nation during 215 years in Egypt, part of the 430 years God said to Abraham.