Some time after this conversation, Joseph was told, “Your father is ill.” He took his two sons, Manasseh and Ephraim, and went to Jacob. When Jacob was told, “Your son Joseph has come,” he roused himself and sat up in bed.
Jacob said to Joseph, “The Strong God appeared to me at Luz in the land of Canaan and blessed me. He said, ‘I’m going to make you prosperous and numerous, turn you into a congregation of tribes; and I’ll turn this land over to your children coming after you as a permanent inheritance.’ I’m adopting your two sons who were born to you here in Egypt before I joined you; they have equal status with Reuben and Simeon. But any children born after them are yours; they will come after their brothers in matters of inheritance. I want it this way because, as I was returning from Paddan, your mother Rachel, to my deep sorrow, died as we were on our way through Canaan when we were only a short distance from Ephrath, now called Bethlehem.” (Isaiah 31:4-9)
The land of the Canaanites belongs to the Jewish people. Among the promises that God gave Abraham, was a promise that the land he was a wanderer in would belong to him and his offspring (Genesis 13:14-17). Later, God gave that same promise to Isaac, and then again to Jacob, to whom twelve sons were born: the fathers of the twelve tribes of Israel. The promise that God gave became increasingly focused; it was not given to all the descendents of Abraham, who was the father not only of Isaac, but also of Ishmael and many others (born to other wives that he married after Sarah’s death). Isaac alone was the son of promise. And the promise did not extend to both sons of Isaac, but only to Jacob and his twelve sons.
For the two sons born to Jacob’s son Joseph, Jacob does something special. He adopts them. They become the equal of his other twelve sons. Why? The descendents of one of his sons, Levi, would be separated from the other tribes of Israel. They would receive no land (Deuteronomy 10:9). By splitting Joseph into two tribes, the land that God gave to the nation of Israel could still be divided twelve ways. Though the Levites were given no territory at all, Joseph would get a double portion, divided between Ephraim and Manasseh.