1 Samuel 26:6
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.
Cross-reference
2 Sam 2:18 identifies Abishai as son of Zeruiah and brother of Joab/Asahel—exact same description as the main verse.
2 Sam 16:9 shows Abishai, son of Zeruiah, offering to kill Shimei—continuing his role as David's loyal supporter.
2 Sam 16:10 David calls Abishai and Joab 'sons of Zeruiah'—directly referencing the same family from the main verse.
2 Sam 18:5 David commands Abishai along with Joab and Ittai—Abishai appears again as a commander.
2 Sam 23:18 describes Abishai, brother of Joab, as a chief of the thirty—same person, expanding his heroic profile.
1 Chronicles 2:16 lists Abishai as son of Zeruiah and brother of Joab, confirming his family background.
1 Chronicles 11:20 identifies Abishai as Joab's brother and a mighty warrior, providing background on the volunteer.
2 Samuel 20:6 shows David again commanding Abishai, this time to pursue Sheba, another instance of their partnership.