Sahih Bukhari
Sahih Bukhari Volume 001, Book 012, Hadith Number 757.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 12. Charecteristics Of Prayer
Narated By Zaid binWahb : Hudhaifa saw a person who was not performing the bowing and prostrations perfectly. He said to him, "You have not prayed and if you should die you would die on a religion other than that of Muhammad."