What does Genesis 48:17 mean?

As Jacob, named Israel by God (Genesis 35:9–11) approaches death, he is blessing two of his grandsons: the oldest sons of Joseph (Genesis 48:1–12). Before Jacob began the prayer of blessing, Joseph had taken great care to arrange his two sons before Jacob so that the old man could put his right hand on the older son's head and his left hand on that of Ephraim, the younger one. Strong customs demanded that it is the oldest son who receives the honor of the greater blessing (Genesis 48:13–16).

Jacob, however, had inexplicably switched his hands to place his right hand on the younger brother's head and his left hand on Manasseh, the oldest. Of course, Jacob is quite old and blind.

At first, Joseph is upset when he realizes what has happened. It's possible he did not realize what happened because he was bowing between his sons at the time; his face might have been down such that he missed what his father was doing. The Hebrew word translated "displeased" is from a similar root term to those translated as "evil." In other words, Joseph is very distressed, even angry. He obviously expected the greater blessing to go to his oldest son. Whether he's angry about which son is more blessed, or the thought that his blind father might have made a mistake, Scripture does not say.

Joseph assumes he just made an odd mistake and now attempts to fix it by physically grabbing Jacob's right hand to move it to Manasseh's head. However, Jacob will make clear in the following verses that this is not an error (Genesis 48:19).