John Gill Commentary Numbers 25:5

"And Moses said unto the judges of Israel, Slay ye every one his men that have joined themselves unto Baal-peor." — Numbers 25:5 (ASV)

And Moses said unto the judges of Israel
Either the same with the heads of the people, or the rulers of thousands, hundreds, fifties, and tens, according to the distribution by the advice of Jethro:

slay you everyone his men, that were joined unto Baalpeor ;
all that were under their several districts and jurisdictions, that were found guilty of that crime; these they are ordered to slay, either with their own hands, or rather cause to be slain by proper persons they should appoint to be executioners.