1 Chronicles 11:19
And said, My God forbid it me, that I should do this thing: shall I drink the blood of these men that have put their lives in jeopardy? for with the jeopardy of their lives they brought it. Therefore he would not drink it. These things did these three mightiest.
David would not drink the water brought from Bethlehem because the three men who fetched it had risked their lives to obtain it for him. He regarded their lives as sacred and would not treat lightly what had been secured at such peril. To satisfy his own thirst with it would have been, in his reckoning, the same as drinking their blood. He therefore refused it for himself and poured it out as an offering to God.