Charles Ellicott Commentary Genesis 48:12

"And Joseph brought them out from between his knees; and he bowed himself with his face to the earth." — Genesis 48:12 (ASV)

He bowed himself. —The Samaritan, Syriac, and Septuagint Versions regard the Hebrew verb as a contracted plural, and many modern commentators adopt this view. It would thus be Manasseh and Ephraim who stood before Jacob with faces bent towards the ground. The pronoun, however, is in favour of the verb being singular, and the sense it gives is equally satisfactory.