A cup of water in the eastern countries was not a matter of small worth.
In India, the Hindus sometimes go a great way to fetch it, and then boil it that it may do the less hurt to travelers when they are hot; and, after that, they stand from morning to night in some great road, where there is neither pit nor rivulet, and offer it, in honor of their god, to be drunk by all passengers. This necessary work of charity, in these hot countries, seems to have been practiced by the more pious and humane Jews; and our Lord assures them that, if they do this in his name, they shall not lose their reward.
Adam Clarke's Commentary, by Adam Clarke