Sahih Muslim Book 5, Hadith Number 2214.

Chapter : Exhortation to Sadaqa even though it is half a date, or a good word. for they are protection against fire.

Abu Huraira reported Allah’s Messenger (may peace be upon him) as saying: O people, Allah is Good and He therefore, accepts only that which is good. And Allah commanded the believers as He commanded the Messengers by saying: “O Messengers, eat of the good things, and do good deeds; verily I am aware of what you do” (xxiii. 51). And He said: ‘O those who believe, eat of the good things that We gave you” (ii. 172) He then made a mention of a person who travels widely, his hair dishevelled and covered with dust. He lifts his hand towards the sky (and thus makes the supplication): “O Lord, O Lord,” whereas his diet is unlawful, his drink is unlawful, and his clothes are unlawful and his nourishment is unlawful. How can then his supplication be accepted?