John Gill Commentary Numbers 31:48

"And the officers that were over the thousands of the host, the captains of thousands, and the captains of hundreds, came near unto Moses;" — Numbers 31:48 (ASV)

And the officers which were over thousands of the host
Over the twelve thousand, of which the host or army consisted: namely, the captains of thousands, and the captains of hundreds, came near unto Moses; of their own accord, without being sent, or required to do what they did.