Why did God tell Jacob not to be afraid to go down into Egypt?

God assured Jacob that Egypt was not a place of danger but of divine purpose: there He would multiply Jacob's descendants into a great nation. This continued the Abrahamic covenant, and Scripture records that Israel indeed became a vast people before Moses led them out.

Les explains that this was a change. Earlier God had told Abraham and Isaac, "Don't go into Egypt," and when they tried it, they got in trouble until they returned to Canaan. Now God tells Jacob, "Don't be afraid to go down into Egypt, for there in Egypt I will make of thee a great nation." Les notes that is exactly what happened: after some 215 years of the children of Israel in Egypt, Moses leads them out as a company of anywhere from 5-7 million people. For that period, they were the biggest nation in the then-known world, the greatest number of any one nation in that part of the world. The Abrahamic covenant is repeated to Isaac, then again to Jacob.

What did God tell Isaac about going into Egypt?

God told Isaac, 'Don't go into Egypt.' The instruction was a prohibition against going down to Egypt. When they tried it, they got into trouble and had to hightail it back to Canaan. This contrasted with God later telling Jacob not to fear going into Egypt, where He would make of him a great nation.