“take his armor.” If one man killed another in battle, the victor could take the armor of the one he killed, and that was to his honor, showing his courage and ability in battle. Sadly, the young man Asahel greatly overestimated his ability. He was so brash and inexperienced that he followed too closely to Abner. Abner, a seasoned warrior and acquaintance of Joab, Asahel’s brother, did not want to kill Asahel and tried to get him to pick a fight with someone else that he might be able to beat. But when Abner could not dissuade Asahel from trying to kill him, because Asahel was so close, Abner was able to simply ram the back end of his spear through Asahel and kill him. The back of the spear was always pointed so it could be stuck in the ground and stay upright.
This is a sad record, because Asahel was likely a good person but inexperienced and overconfident; Abner did not want to kill him, and later Asahel’s brother Joab killed Abner.