سورة البقرة

The Messenger of Allah (peace be upon him and his family): Whoever does good to a believer and then hurts him with words or reminds him of his favour, Allah surely nullifies his charity.

Ali ibn Ibrahim (may Allah have mercy on him): If a person places excessive obligation upon and injures one to whom he has given charity, his charity is nullified — just like the disappearance of dust that lies upon a "safwan." Safwan is a large, smooth rock in the desert. The rain falls, washes the dust from it and carries it away. Allah has given this parable for one who does a good deed and then destroys it by the reminder of favour and the injury that he inflicts afterwards.

The Prophet (peace be upon him and his family): When a needy person makes a request, do not cut off his speech about his need until he finishes it. Then either fulfil his need with calmness, gentleness and respect, or turn him away in a beautiful manner [without ill conduct or ill speech]. Allah [sometimes] sends toward you those who are neither human nor jinn, to see how you behave regarding what He has granted you. He is beyond need of your charities and all of your acts of obedience. Allah does not command you to give charity or perform acts of obedience because He has any need of them; rather, He gives you such a command and calls you to it because of your need for their reward. Allah is Forbearing — He does not hasten in punishing you. And it is said: He does not hasten in punishing one who places obligation upon another and injures him with his charity. And had Allah not been Forbearing, Praiseworthy and All-Knowing, He would not have bestowed favour.