Hazrat Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah[SAWW](PBUH) said, "O people! Allah is Pure and, therefore, accepts only that which is pure. Allah has commanded the believers as He has commanded His Messengers by saying: `O Messengers! Eat of the good things, and do good deeds.’ (23:51) And He said: `O you who believe (in the Oneness of Allah – Islamic Monotheism)! Eat of the lawful things that We have provided you…”’ (2:172). Then he [SAWW](PBUH) made a mention of the person who travels for a long period of time, his hair are disheveled and covered with dust. He lifts his hand towards the sky and thus makes the supplication: `My Rubb! My Rubb!’ But his food is unlawful, his drink is unlawful, his clothes are unlawful and his nourishment is unlawful, how can, then his supplication be accepted?”
[Muslim Hadith # 2214].