1 Samuel 26:4-6

4 he sent spies and found out that Saul was indeed there.

5 He went at once and located the exact place where Saul and Abner son of Ner, commander of Saul's army, slept. Saul slept inside the camp, and his men camped around him.

6 Then David asked Ahimelech the Hittite, and Abishai the brother of Joab (their mother was Zeruiah), "Which of you two will go to Saul's camp with me?" "I will,"Abishai answered.