2 Samuel 3:26-28 English Standard Version (ESV)

26. 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.

27. And when Abner returned to Hebron, Joab took him aside into the midst of the gate to speak with him privately, and there he struck him in the stomach, so that he died, for the blood of Asahel his brother.

28. Afterward, when David heard of it, he said, “I and my kingdom are forever guiltless before the Lord for the blood of Abner the son of Ner.

2 Samuel 3