Charles Ellicott Commentary 2 Samuel 2:27

"And Joab said, As God liveth, if thou hadst not spoken, surely then in the morning the people had gone away, nor followed every one his brother." — 2 Samuel 2:27 (ASV)

Unless you had spoken. — Joab’s reply to Abner allows for either of two interpretations:

1. Joab seeks to throw the whole blame of the conflict upon Abner, by saying that if he had not proposed the combat between the champions (2 Samuel 2:14), there would have been no battle, but “the people” of both sides would have separated peaceably at Gibeon.
2. Alternatively, as the phrase is more generally and more probably understood, Joab had intended to keep up the pursuit only until the following morning, but since Abner already sued for mercy, he was content and would stop now.