Adam Clarke on Genesis 48:18

Joseph said - Not so, my father - Joseph supposed that his father had made a mistake in laying his right hand on the head of the youngest, because the right hand was considered as the most noble, and the instrument of conveying the highest dignities, and thus it has ever been considered among all nations, though the reason of it is not particularly obvious. Even in the heavens the right hand of God is the place of the most exalted dignity. It has been observed that Joseph spoke here as he was moved by natural affection, and that Jacob acted as he was influenced by the Holy Spirit.