Poured it out unto the Lord - To make libations, both of water and wine, was a frequent custom among the heathens. We have an almost similar account in Arrian's Life of Alexander: "When his army was greatly oppressed with heat and thirst, a soldier brought him a cup of water; he ordered it to be carried back, saying, I cannot bear to drink alone while so many are in want, and this cup is too small to be divided among the whole." Tunc poculo pleno sicut oblatum est reddito: Non solus, inquit, bibere sustineo, nec tam exiguum dividere omnibus possum. - Arrian, lib. vi.
The example was noble in both cases, but David added piety to bravery; he poured it out unto the Lord.

And the three mighty men brake through the host of the Philistines,.... Which lay in the valley of Rephaim, between the hold in which David was and the well of Bethlehem; these three men hearing David express himself in the above manner, though without any view that any should risk their lives to obtain it, only in a general way said, oh for a draught of the water of the well of Bethlehem! immediately set out, and made their way through the army of the Philistines to the well:

and drew water out of the well of Bethlehem, that was by the gate,

and took it, and brought it to David; in a vessel which they probably carried with them for that purpose:

nevertheless he would not drink thereof; because, say they who take these words in a spiritual sense, it was not this water, but spiritual water, he desired: but the reason is given in Sa2 23:17,

but poured it out unto the Lord; as a libation to him, it being rather blood than water, being fetched at the hazard of men's lives, and therefore more fit to be offered as a sacrifice to God than to be drank by him; and this he might do in thankfulness to God for preserving the lives of the men. Gersom thinks it was now the feast of tabernacles, which was the feast of ingathering the fruits of the earth, when great quantities of water were drawn and poured out at the altar, which was done to obtain the blessing of the former rain; See Gill on Joh 7:37 and See Gill on Joh 7:38.