2 Samuel 2:23
Howbeit he refused to turn aside: wherefore Abner with the hinder end of the spear smote him under the fifth rib, that the spear came out behind him; and he fell down there, and died in the same place: and it came to pass, that as many as came to the place where Asahel fell down and died stood still.
Cross-reference
2 Samuel 3:27
Historical context
2 Samuel 3:27 shows Joab avenging Asahel's death by killing Abner — the direct consequence of this verse.
2 Samuel 20:10
Parallel
2 Samuel 20:10 describes Joab killing Amasa with a belly strike — similar sudden death by a commander, echoing Abner's killing of Asahel.