What Does Genesis 48:18 Mean?

And Joseph said to his father, "Not this way, my father; since this one is the firstborn, put your right hand on his head." The verbal correction accompanies the physical attempt to redirect the hand: "Not this way." Joseph explains his objection: Manasseh is the firstborn; the right hand belongs on his head. The explanation is respectful ("my father") and factual (Manasseh is the firstborn). Joseph is not challenging his father's authority but his information: he thinks the old man has made the wrong placement due to dim eyesight and perhaps confusion about which boy is which.

The scene where Joseph says "not this way, my father" in the context of a blessing scene echoes Isaac's misdirected blessing of Jacob in Genesis 27. In Genesis 27, the wrong son received the wrong blessing deliberately because the blessing-giver was deceived (Isaac thought Jacob was Esau). In Genesis 48, Jacob is not deceived: he knows which boy he is blessing with which hand. The echo is exact in structure (patriarch blessing, hand positioning, confusion over which son receives greater blessing) and opposite in mechanism (deception in ch.27, deliberate reversal in ch.48).

"Put your right hand on his head": Joseph's corrective instruction is the reasonable response to what looks like an error. The right hand on the firstborn's head is the conventional expectation; Joseph is asking for the conventional. The dying patriarch's deliberately unconventional response (verse 19) will override the correction and explain why the conventional arrangement is not what God intends for Ephraim and Manasseh.