Charles Ellicott Commentary Judges 20:31

"And the children of Benjamin went out against the people, and were drawn away from the city; and they began to smite and kill of the people, as at other times, in the highways, of which one goeth up to Beth-el, and the other to Gibeah, in the field, about thirty men of Israel." — Judges 20:31 (ASV)

To smite of the people, and kill. —Rather, to smite the wounded or beaten of the people. This apparently means that when some of the Israelites had been wounded with slings, the Benjamites began to rush on them to kill them. They feigned flight along two highways: one leading to Bethel, and the other to a place that, to distinguish it from Gibeah, seems to have been called “Gibeah in the field.” In this feigned flight, thirty Israelites were killed.

“Gibeah in the field” seems to be Jeba. The main road from Gibeah (Tuleil el Fûl), at about a mile’s distance from the hill, branches off into two roads: one leading to Beitin (Bethel), and the other to Jeba (“Gibeah in the field”).

The highways. —(Mesilloth.) Roads like the Roman viae regiae, regularly built.