Adam Clarke on Genesis 48:15

He blessed Joseph - The father first, and then the sons afterwards. And this is an additional proof to what has been adduced under Gen 48:12, of Jacob's superiority; for the less is always blessed of the greater.

The God which fed me all my life long - Jacob is now standing on the verge of eternity, with his faith strong in God. He sees his life to be a series of mercies; and as he had been affectionately attentive, provident, and kind to his most helpless child, so has God been unto him; he has fed him all his life long; he plainly perceives that he owes every morsel of food which he has received to the mere mercy and kindness of God.