בראשית מח:יג פירוש: רש״י, רשב״ם, רד״ק ורבנו בחיי

את אפרים בימינו משמאל ישראל EPHRAIM ON HIS RIGHT HAND TOWARDS ISRAEL’S LEFT — If one is moving towards another person his right hand is opposite the other’s left. Now since he (Manasseh) was the first-born he was marked out for the blessing and should have been placed at Jacob’s right hand.

את אפרים בימינו, in order to place him on Israel’s left side, (seeing he was the younger).

בימינו, on Joseph’s right, which was the left side of Yaakov (Yisrael)