The events recorded in the last three chapters of Genesis deal with the last days of Jacob and Joseph. In these last chapters there are many other references to earlier episodes in the book.
"This constant harking back to earlier episodes and promises is totally in place in a book whose theme is the fulfillment of promises, a book that regularly uses analogy between episodes as a narrative technique. And at the close of a book it is particuarly [sic] appropriate to exploit these cross-linkages to the full. It reinforces the sense of completeness and suggests that the story has reached a natural stopping point."911
This very important section explains how Ephraim and Manasseh came to have equal standing with Joseph's brothers and why Joseph did not become the head of a tribe.
Manasseh would have been between 20 and 26 years old at this time (41:50; 47:28). Ephraim, of course, was younger.
It was as Israel, the prince with God, that Jacob performed this official and significant act (vv. 2-4; cf. Heb. 11:21). His action was in harmony with God's will and purpose for the chosen family, and it involved the patriarchal promises to which he referred (cf. 35:10-12).
"Jacob may be losing his health, but he is not losing his memory. He can recall the incident of many years earlier when God appeared to him at Luz [Bethel] (35:9-15). He repeats the promises of God about fertility, multiplication, that his seed will be an assembly of nations, and finally the promise of land. The only essential element of that theophany he does not repeat is the name change from Jacob to Israel. In this way, Jacob minimizes his role and maximizes God's role in that event."912
By adopting Joseph's first two sons as his own and giving them equal standing with Joseph's brothers, Jacob was bestowing on Joseph the double portion of the birthright (v. 5; cf. v. 22; 1 Chron. 5:1-2). He was also in effect elevating Joseph to the level of himself. Joseph was the first son of Jacob's intended first wife. Jacob's reference to Rachel (v. 7) shows that she, as the mother of Joseph, was in his mind in this act. This act honored her. The other sons of Joseph received their own inheritances.
"Verse 7 has long puzzled biblical interpreters. Why the mention of Rachel at this point in the narrative, and why the mention of her burial site? If we relate the verse to what precedes, then the mention of Rachel here could be prompted by the fact that just as she had borne Jacob two sons' (44:27, Joseph and Benjamin) at a time when he was about to enter (48:7) the land, so also Joseph gave Jacob two sons' (v. 5) just at the time when he was about to enter Egypt."913