Albert Barnes Commentary Judges 20:18

"And the children of Israel arose, and went up to Beth-el, and asked counsel of God; and they said, Who shall go up for us first to battle against the children of Benjamin? And Jehovah said, Judah [shall go up] first." — Judges 20:18 (ASV)

Went up to the house of God - It should be “to Bethel.” At this time the ark was at Bethel (Compare to 1 Samuel 10:3), and not at Shiloh. It is not unlikely that though Shiloh was the chief residence of the ark (Jeremiah 7:12), yet the tabernacle, being moveable, was, either at stated times, or as occasion required, moved to where the Judge resided, or the congregation assembled (Compare to 1 Samuel 7:16). On the present occasion the ark may have been moved to Bethel for the convenience of proximity to the great national council at Mizpeh.