2 Samuel 2:19

And Asahel pursued after Abner; and in going he turned not to the right hand nor to the left from following Abner.

Cross-reference

2 Samuel 2:21 directly continues the narrative: Abner tells Asahel to turn aside, but he refuses to stop pursuing.

2 Samuel 3:27 Historical context

2 Samuel 3:27 records Joab's revenge for Asahel's death—the pursuit begun here leads to Abner's murder.

2 Samuel 3:30 Historical context

2 Samuel 3:30 explicitly states Joab and Abishai killed Abner because he killed Asahel—this pursuit sets the tragic chain in motion.