Albert Barnes Commentary 1 Chronicles 2:6

"And the sons of Zerah: Zimri, and Ethan, and Heman, and Calcol, and Dara; five of them in all." — 1 Chronicles 2:6 (ASV)

The sons of Zerah - Here, for the first time, the writer of Chronicles draws from sources not otherwise known to us, recording facts not mentioned in the earlier Scriptures. Ethan, Heman, Calcol, and Dara, sons of Zerah, are only known to us from this passage, since there are no sufficient grounds for identifying them with the “sons of Mahol” (marginal reference).