Albert Barnes Commentary Judges 21:10

"And the congregation sent thither twelve thousand men of the valiantest, and commanded them, saying, Go and smite the inhabitants of Jabesh-gilead with the edge of the sword, with the women and the little ones." — Judges 21:10 (ASV)

And the congregation sent 12,000 men - A thousand from each tribe; they followed the precedent of (Numbers 31:4).