Sahih al-Bukhari 808
Sahih al-Bukhari · Book 10: Call to Prayers (Adhaan) · If one does not perform the prostrations perfectly
Narrated Abu Wail:
حَدَّثَنَا الصَّلْتُ بْنُ مُحَمَّدٍ ، قَالَ حَدَّثَنَا مَهْدِيٌّ ، عَنْ وَاصِلٍ ، عَنْ أَبِي وَائِلٍ ، عَنْ حُذَيْفَةَ ، رَأَى رَجُلاً لاَ يُتِمُّ رُكُوعَهُ وَلاَ سُجُودَهُ، فَلَمَّا قَضَى صَلاَتَهُ قَالَ لَهُ حُذَيْفَةُ مَا صَلَّيْتَ ـ قَالَ وَأَحْسِبُهُ قَالَ ـ وَلَوْ مُتَّ مُتَّ عَلَى غَيْرِ سُنَّةِ مُحَمَّدٍ صلى الله عليه وسلم.
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 (ﷺ) Muhammad."