Zerujah — David's sister. His father is not named either because he was now dead; or because he was an obscure person.
Related Commentaries of 1 Samuel 26:6
1 Samuel 26:6
6 Then answered David and said to Ahimelech the Hittite, and to Abishai the son of Zeruiah, brother to Joab, saying, Who will go down with me to Saul to the camp? And Abishai said, I will go down with thee.