Adam Clarke on 2 Samuel 23:16

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.