Hudhaifa saw a person who was not performing the bowing and prostration 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."
Reference: Sahih al-Bukhari 791 In-book : Book 10, Hadith 186 USC-MSA web (English) : Vol. 1, Book 12, Hadith 757 (deprecated)
Help us gift a modern, ad-free Islamic application for the Muslim Ummah. Your donation will be recorded as Sadaqah Jariyah in your book of deeds, In Sha Allah.