Prayers (Salat)
Bukhari :: Book 1 :: Volume 8 :: Hadith 372
Narrated 'Uqba bin 'Amir:
The Prophet was given a silken Farruj as a present. He wore it while praying. When he had finished his prayer, he took it off violently as if with a strong aversion to it and said, "It is not the dress of Allah-fearing pious people."