Sahih Al Bukhari Hadith Number 808

Narrated Abu Wail: Hudhaifa said, “I saw a person not performing his bowing and prostrations perfectly. When he completed the prayer, I told him that he had not prayed.” I think that Hudhaifa added (i.e. said to the man), “Had you died, you would have died on a tradition other than that of the Prophet (peace be upon him) Muhammad.”

10  Call to Prayers (Adhaan)
Hadith number 808
Volume no 1
Chapter: 132 (If one does not perform the prostrations perfectly)