Ramban on Genesis 48:20/רמב"ן על בראשית מ״ח:כ׳

1AND HE BLESSED THEM THAT DAY. The meaning of that day is that since Joseph had urged him to give Menasheh precedence, the verse declares that Jacob did not wish to remove his right hand from Ephraim’s head to that of Menasheh. Moreover, he expressly reiterated on that occasion, in Joseph’s presence, when he blessed them by saying, As Ephraim and Menasheh. And he put Ephraim before Menasheh in all his blessings.

2BY THEE SHALL ISRAEL BLESS. Jacob addressed this to Joseph. It means that the nation of Israel will bless with your children and say to those being blessed, God make thee as Ephraim and Menasheh.