26 Joab then left David and sent messengers after Abner, and they brought him back from the cistern at Sirah. But David did not know it.

Read 2 Samuel 3:26 Using Other Translations

And when Joab was come out from David, he sent messengers after Abner, which brought him again from the well of Sirah: but David knew it not.
When Joab came out from David's presence, he sent messengers after Abner, and they brought him back from the cistern of Sirah. But David did not know about it.
Joab then left David and sent messengers to catch up with Abner, asking him to return. They found him at the well of Sirah and brought him back, though David knew nothing about it.