It is narrated from Sayyiduna Abu Buhaysah (may Allah be pleased with him) that he said: I came to the Prophet (peace and blessings be upon him). I slipped in between him (peace and blessings be upon him) and his shirt and clung to him (peace and blessings be upon him), and 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." I said: O Messenger of Allah, what is the thing that it is not lawful to withhold? He (peace and blessings be upon him) said: "Salt." I said: 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."
Hadith Referenceالمعجم الكبير للطبراني / مسند من يعرف بالكنى / 18993