John Gill Commentary Numbers 31:13

"And Moses, and Eleazar the priest, and all the princes of the congregation, went forth to meet them without the camp." — Numbers 31:13 (ASV)

And Moses and Eleazar the priest, and all the princes of the
congregation
Attended, no doubt, with a proper retinue:

went forth to meet them without the camp ;
partly to do honour to them, and to congratulate them on their victory, and partly to hinder them going into the camp directly, until they were purified; see (Genesis 14:17Genesis 14:18) .