John Gill Commentary Judges 21:5

"And the children of Israel said, Who is there among all the tribes of Israel that came not up in the assembly unto Jehovah? For they had made a great oath concerning him that came not up unto Jehovah to Mizpah, saying, He shall surely be put to death." — Judges 21:5 (ASV)

And the children of Israel said
One to another, after they had offered their sacrifices, and while they were together in Shiloh:

who is there among all the tribes of Israel, that came not up with the
congregation to the Lord ?
when they were summoned to come to Mizpeh, to consult together about the affair of the Levite's concubine, as appears by what follows:

for they had made a great oath ;
in a very awful and solemn manner, with a curse annexed to it, as that about not giving a wife to Benjamin, (Judges 21:18)

concerning him who did not come up to the Lord to Mizpeh :
not about him who did not go out to battle against Benjamin, nor about every individual who did not come to consult about it; but every city that did not send their proper representatives or quota to assist in that affair:

he shall surely be put to death ;
this was sent along with the summons, in order to quicken their attention to them.