Matthew Poole and continuators on Genesis 48:20

20 And he blessed them in that day, saying, In thee shall Israel bless, saying, God make thee as Ephraim, and as Manasseh: and he set Ephraim before Manasseh.

(i. e.) In thy seed, as appears both from the relative, them, here, and from ver. 15. where his blessing of them is called the blessing of Ioseph, and from the following words, where this is interpreted of Ephraim and Manasseh. And in thee, or in thy seed, i. e. using their names in the form or words of blessing, as eminent examples of blessedness.