Jamieson, Fausset and Brown on Judges 21:17

17. There must be an inheritance for them that be escaped of Benjamin--As they were the only rightful owners of the territory, provision must be made for transmitting it to their legitimate heirs, and a new act of violence was meditated (Jud 21:19); the opportunity for which was afforded by the approaching festival--a feast generally supposed to be the feast of tabernacles. This, like the other annual feasts, was held in Shiloh, and its celebration was attended with more social hilarity and holiday rejoicings than the other feasts.