Albert Barnes Commentary Judges 5:16

"Why sattest thou among the sheepfolds, To hear the pipings for the flocks? At the watercourses of Reuben There were great searchings of heart." — Judges 5:16 (ASV)

Great searchings - (thoughts, Judges 5:15) of heart Deborah means to say that at first the Reubenites made magnanimous resolutions to help their brothers against Jabin. But they stayed at home, and let the opportunity slip.