Sayyidah Buhaysah (may Allah be pleased with her) said: My father asked the Prophet (peace and blessings be upon him) for permission to enter between his (peace and blessings be upon him) (body) and his shirt. He (peace and blessings be upon him) gave him permission, so he entered from behind between his (peace and blessings be upon him) (body) and his shirt, and began embracing him (peace and blessings be upon him) and pressing his chest against the back of the Prophet (peace and blessings be upon him). Then he said: O Messenger of Allah, what is the thing that it is not lawful to withhold? He (peace and blessings be upon him) said: "Water." The questioner asked: O Messenger of Allah, what is the thing that it is not lawful to withhold? He (peace and blessings be upon him) said: "Salt." He asked again: O Messenger of Allah, what is the thing that it is not lawful to withhold? He (peace and blessings be upon him) said: "If you do good, it is better for you." And his (peace and blessings be upon him) words ended at water and salt. She said: So that man (my father) would not withhold any water, however little it was.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20898