John Gill Bible Commentary

And it came to pass on the morrow, that the people rose early,.... The day after their fasting and prayer, and a sense of their present case and circumstances being deeply impressed upon their minds, they rose early in the morning to acts of devotion, and exercises of religion, hoping that being in the way of their duty, the difficulties with which they were perplexed would be removed: and built there an altar; if this place was Bethel, as Kimchi reasons, there Jacob had built an altar; but that in such a course of years might have been demolished: and if it was Shiloh, there was the tabernacle, and so the altar of the Lord there; wherefore this either signifies the repairing of that, being in ruins, which is not likely, since it was but lately used, Jdg 20:26 or the building of a new one, which to do in the tabernacle was not unlawful, especially when the number of sacrifices required it, which it is highly probable was the case now, as it was at the dedication of the temple, Kg1 8:64 though the above mentioned writer thinks, that building an altar signifies, as in many places, only seeking the Lord; but the use for which it was built is expressed: and offered burnt offerings and peace offerings; both to atone for the sins they had been guilty of in the prosecution of the war, and to return thanks for victory given, and to implore fresh favours to be bestowed upon them.