John Calvin Reformed @genevareformer

15. God before whom. Although Jacob knew that a dispensation of the grace of God was committed to him, in order that he might effectually bless his grandchildren; yet he arrogates nothing to himself, but suppliantly resorts to prayer, lest he should, in the least degree, detract from the glory of God.

Matthew Henry Presbyterian @wholebiblehenry

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

John Gill Reformed Baptist @doctorgill

And he blessed Joseph,.... In his sons who were reckoned for him, and became the heads of tribes in his room: and said, God before whom my fathers Abraham and Isaac did walk; in whom they believed, whom they professed, and whom they feared, served, and worshipped, and with whom they had communion: the God which fed me all my long unto this day; who...