Mishkat al-Masabih 3007

‘A’isha said she asked God's Messenger what the thing was which it was unlawful to refuse and he replied that it was water, salt and fire. She said, “Messenger of God, we know about water, but what is the significance of salt and fire?” He replied, “Little rosy one, he who gives fire is as though he had given sadaqa of all that that fire cooked ; he who gives salt is as though he had given sadaqa of all that that salt freshened ; he who gives a Muslim a drink of water where water is found is as though he had set free a slave; and he who gives a Muslim a drink of water where water is not found is as though he had given him life.” Ibn Majah transmitted it.