Asahel
The youngest of Zeruiah's three sons, brother of Joab and Abishai, and as swift of foot as a wild gazelle. At the battle by the pool of Gibeon he pursued Abner and would not turn aside for anyone else. Abner twice warned him off, unwilling to face Joab afterwards, then struck backwards with the butt of his spear, which went through his stomach. Asahel's death is why Joab later murdered Abner at Hebron.
What we know — and how we know it
Where in scripture
2 SamuelThe three sons of Zeruiah were there, Joab, and Abishai, and Asahel: and Asahel was as light of foot as a wild gazelle.
2 Samuel 2:18 — Swift as a wild gazelle
However he refused to turn away. Therefore Abner with the back end of the spear struck him in the body, so that the spear came out behind him; and he fell down there, and died in the same place. As many as came to the place where Asahel fell down and died stood still.
2 Samuel 2:23 — Killed by Abner
Scripture quotations are from the World English Bible, a public-domain translation.
Family
In their own words — 1 recorded saying
“Then Abner, looking back, said, Is it you, Asahel? And he said, It is I.” — 2 Samuel 2:20
Speaker attribution: Clear Bible MACULA (CC BY 4.0). Wording: Bible in Basic English (public domain).