When Joseph saw that his father had placed his right hand on Ephraim’s head, he was displeased and took his father’s hand to move it from Ephraim’s head to Manasseh’s.
17. And when Joseph saw. Because by crossing his arms, Jacob had so placed his hands as to put his left hand upon the head of the first-born, Joseph wished to correct this proceeding, as if it had been a mistake.
Here is, I. The blessing with which Jacob blessed the two sons of Joseph, which is the more remarkable because the apostle makes such particular mention of it (Heb 11:21), while he says nothing of the blessing which Jacob pronounced on the rest of his sons, though that also was done in faith. Observe here, 1. Jacob was blind for age, Gen 48:10.
Commenting on Genesis 48:8-22
And when Joseph saw that his father laid his right hand upon the head of Ephraim, it displeased him,.... To see the younger preferred to the elder; parents, generally speaking, having the greatest regard to the firstborn with respect to honour and estate, and to them, in those times, the patriarchal blessing particularly was thought to belong; but it did not always go to them...