The Book of Zakat (Kitab Al-Zakat)
Muslim :: Book 5 : Hadith 2214
Abu Huraira reported Allah's Messenger (may peace be upon him) as saying: 0 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: ' 0 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,0 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?