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? Abishai said, I will go down with you.
and to Abishai the son of Zeruiah, brother to Joab; Zeruiah was the sister of David, 1 Chronicles 2:15; and these were two sons of hers, who very probably joined David at the cave of Adullam, 1 Samuel 22:1;