John Gill Commentary Genesis 49:2

"Assemble yourselves, and hear, ye sons of Jacob; And hearken unto Israel your father." — Genesis 49:2 (ASV)

Gather yourselves together This is repeated to hasten them, and to suggest that he had something of importance to make known to them, which he chose to do when they were together:

and hear, you sons of Jacob, and hearken to Israel your father: these words are used and doubled to excite their attention to what he was about to say, and which is urged because of the near relation between them.