C. F. Keil and Franz Delitzsch on Judges 20:27-28

Jdg 20:27-28

Having made these preparations, they inquired of the Lord whether they should continue the war, and received this reply: “Go up (against Benjamin); for to-morrow I will give it unto thy hand” (ידך, the hand of the congregation carrying on the war). To this the supplementary remark is appended, that the ark of the covenant was at Bethel in those days, and the high priest served before it. The expression “in those days” implies that the ark of the covenant was only temporarily at Bethel, and therefore had been brought thither from the tabernacle at Shiloh during this war.The Victory on the Third Day’s Engagement. - Jdg 20:29. The account of this commences with the most important point, so far as their success was concerned: Israel set liers in wait (troops in ambush) round about Gibeah.