Albert Barnes Commentary 2 Samuel 3:26

"And when Joab was come out from David, he sent messengers after Abner, and they brought him back from the well of Sirah: but David knew it not." — 2 Samuel 3:26 (ASV)

The well of Sirah — This location is not mentioned anywhere else in Scripture. According to the historian Josephus, it was located about two and a half miles from Hebron.