John Gill Commentary Judges 21:13

"And the whole congregation sent and spake to the children of Benjamin that were in the rock of Rimmon, and proclaimed peace unto them." — Judges 21:13 (ASV)

And the whole congregation sent some to speak to the children
of Benjamin
Sent some messengers to them, to call them, and desire them to come to them:

that were in the rock Rimmon ;
the six hundred men who had hid themselves in a cave in it, of which the people of Israel were informed:

and to call peaceably unto them ;
to proclaim peace to them, and assure them of it, and to let them know that they had no ill design against them, that they might come safely to them, and would be kindly received and protected by them.