Of the children of Perez. — The reference is to Jashobeam. He belonged to the branch of Judah called Perez, or Pharez, to which David himself belonged.
The chief of all the captains of the host for the first month. — This notice about Jashobeam is obscure. The “captains of the host” (Heb., hosts) seem to be the twelve generals of division. (Comp. 1 Chronicles 27:5.) Jashobeam, as the first of David’s heroes, may have enjoyed a kind of precedence among the commanders of the army corps; although he was not commander-in-chief of the entire national forces, which was the function of Joab. Or perhaps it is meant merely to emphasise the fact that Jashobeam was “the first” in the rotation of the generals; so that the phrase “for the first month” explains what precedes it. Or “the captains of the hosts” may possibly mean the officers of the subdivisions of the first army corps, of whom Jashobeam was, of course, the chief. The context appears to favour this last explanation.