Three — They were ten, Genesis 46:25, and five of them are named, 1 Chronicles 8:1, but here only three are mentioned, either because these were most eminent; or because the other families are now extinct.
Related Commentaries of 1 Chronicles 7:6
1 Chronicles 7:6
6 The sons of Benjamin; Bela, and Becher, and Jediael, three.