Hazrat Ubayy bin Ka'b (may Allah be pleased with him) taught a blind person, and after that, whenever he (the blind person) would come to him, he would feed him. Hazrat Ubayy bin Ka'b (may Allah be pleased with him) says that some doubt arose in my heart regarding this matter, so I asked the Messenger of Allah (peace and blessings be upon him) about it. The Prophet (peace and blessings be upon him) said: If he gives you that thing as a gift (wage), then there is no good in it for you, but if it is for your own food and for your family, then there is no harm in accepting it.