It is narrated from Sayyiduna Ruwayfi' bin Thabit al-Ansari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "It is not lawful for anyone who believes in Allah and the Last Day, or: whoever believes in Allah and the Last Day, to give his water to another man's child."
Hadith Referenceالمعجم الكبير للطبراني / باب الراء / 4474