Albert Barnes Commentary 1 Samuel 7:6

"And they gathered together to Mizpah, and drew water, and poured it out before Jehovah, and fasted on that day, and said there, We have sinned against Jehovah. And Samuel judged the children of Israel in Mizpah." — 1 Samuel 7:6 (ASV)

Two rites are brought together here that belong especially to the Feast of Tabernacles and the Day of Atonement, respectively: drawing and pouring out water, and fasting. For this reason, some think that Samuel chose the Feast of Tabernacles, and the fast that preceded it, as the occasion for assembling the people. Others explain the pouring out of water as symbolizing the pouring out of the heart in penitence, as if it were water; as a symbolic act expressing their ruin and helplessness (2 Samuel 14:14); or as typifying their desire that their sins might be forgotten, as waters that pass away (Job 11:16).

The phrase And Samuel judged appears to mark the beginning of his civil and military judgeship, which started at Mizpah on this occasion. As a civil judge, he did exactly what Moses did (Exodus 18:13–16). As a military judge, he did what Othniel, Ehud, Barak, and Gideon had done before him: he organized and marshalled the people for effective resistance against their oppressors and led them to victory.