Isaac was prohibited by God from going down to Egypt and was also protected secretly with his wife by God (26:2, 6-11). Egypt is a type of the world. Going down to the world is a big temptation to the believers. For Abraham's descendant to go down to Egypt signifies the believers in Christ going down to the world.
Isaac waxed great and grew more and more until he became very rich, having flocks, herds, and a great household. He became much mightier than others, and God made room for him that he might be fruitful in the land (26:12-22). The prosperity of Isaac was not for himself but for the fulfillment of God's purpose.
God appeared to Isaac again and promised as the God of Abraham to be with him, to bless him, and to multiply his seed for the sake of His servant Abraham (26:24-25).
As a whole, God made Isaac an heir to inherit all that his father had and blessed him all the way in peace and prosperity. Isaac was a person of inheritance and of a pleasant, enjoying life. The only trouble he experienced was due to his wife, but God protected him with his wife secretly.
God loved Jacob and chose Jacob (Mal. 1:2b; Rom. 9:10-13).
God raised Jacob as an heir to Abraham and to Isaac to inherit God's promise to them and God's covenant with them (Gen. 28:13-14).