John Gill 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)

The whole number of the chief of the fathers of the mighty men
of valour were two thousand six hundred .
] Who were the commanders and principal officers of his army; and such a number supposed a large army, as follows.