Israel’s inquiry shows a loss of confidence because of their first defeat. They are doubting the rightness of their cause, of continuing with the war, as suggested by their reference to Benjamin as our brothers.
But as they have already re-formed the battle line (Judges 20:22), their inquiry is insincere; they want to press on against their brothers.1
23 And the people of Israel went up and wept before the LORD until the evening. And they inquired of the LORD, “Shall we again draw near to fight against our brothers, the people of Benjamin?” And the LORD said, “Go up against them.”