2 Samuel 23:13-17
And three of the thirty chief men went down, and came about harvest time to David at the cave of Adullam, when a band of Philistines was encamped in the valley of Reph'aim. David was then in the stronghold; and the garrison of the Philistines was then at Bethlehem. And David said longingly, "O that some one would give me water to drink from the well of Bethlehem which is by the gate!"
Then the three mighty men broke through the camp of the Philistines, and drew water out of the well of Bethlehem which was by the gate, and took and brought it to David. But he would not drink of it; he poured it out to the LORD, and said, "Far be it from me, O LORD, that I should do this. Shall I drink the blood of the men who went at the risk of their lives?" Therefore he would not drink it. These things did the three mighty men.