Genesis 48:6

Jacob begins by reciting to Joseph God's grant of the land of Canaan. This set out the family estate, the property he had to leave among his children. He then adopts the sons of Joseph. This was needed to give them the rights of children, because in a great legal sense they were strangers to Abraham. Their mother was an Egyptian. They were a seed, therefore, whom the law would, in its day, have put away. But Jacob adopts them. He takes them into the family… They are established as the seed of Abraham, and made children of Jacob.

Scripture confirms this. 1 Chronicles 5:2 tells us, concerning Israel, that "the birthright belonged to Joseph." Verse 1 tells us that the birthright of Reuben, the eldest son, "was given to the sons of Joseph the son of Israel." We can see why Joseph had two sons and only two: so that he might have the double portion of the firstborn. So in the dividing of the land, each of Israel's sons (Levi excluded for obvious reasons) had a single portion, that is one tribe each. Joseph had the double portion, two tribes, Ephraim and Manasseh.

The genealogies show that families were all counted under one head, if they were not large enough to make a distinct family (1 Chronicles 23:10-11). Or they might come in as two, when strictly the head should have been only one, as with Ephraim and Manasseh. If Joseph had had a dozen sons afterwards, they would not have formed distinct families (Genesis 48:6). They would have merged into the tribes of Ephraim and Manasseh.

The adoption of Joseph's sons is interesting and instructive. As the offspring of the Gentile wife Asenath they were in danger of becoming absorbed into the nations and so forgetting their father's house. Jacob prevented this by adopting the sons. It was an action of faith. "By faith Jacob, when dying, blessed each of the sons of Joseph, bowing in worship over the head of his staff" (Hebrews 11:21).

This was not just a whim of Jacob's old age, but history has proved it to be an important matter. Jacob had 12 sons at the time, the exact number of administrative completeness. Why should he give Joseph an extra place among the tribes by naming them after his two sons? The wisdom of God was in this. Later we find that Levi received no distinctive inheritance among the tribes (Numbers 1:47-53). That was because the tribe was set apart to do the service of God in the tabernacle and among all the tribes.

Joseph is unknown to his brothers, or at best only a memory. Meanwhile he is in power in Egypt, and marries Asenath, an Egyptian woman. His sons are cut off from their mother's Gentile connection. They are moved into the position of "heirs of the promise" with faithful Abraham, rightly counted with Israel, and they divide the inheritance with them. So the Lord Jesus, rejected by the Jews, has called out children from among the nations.