Albert Barnes Commentary 1 Kings 2:33

"So shall their blood return upon the head of Joab, and upon the head of his seed for ever: but unto David, and unto his seed, and unto his house, and unto his throne, shall there be peace for ever from Jehovah." — 1 Kings 2:33 (ASV)

Upon the head of his seed — Compare the marginal reference. Nothing further is heard of Joab’s descendants in the history.