Charles Ellicott Commentary 2 Chronicles 26:12

"The whole number of the heads of fathers` [houses], even the mighty men of valor, was two thousand and six hundred." — 2 Chronicles 26:12 (ASV)

Chief of the fathers. — Heads of the families, or father-houses.

Of the mighty men of valour. — Namely, the mighty men of valour, in apposition with heads of the families. The army was marshalled, as was customary, according to clans, or houses, the heads of which are here distinguished as “valiant heroes.”