Sahih al-Bukhari 791
Sahih al-Bukhari · Book 10: Call to Prayers (Adhaan) · Not performing bowing perfectly
Narrated Zaid bin Wahb:
حَدَّثَنَا حَفْصُ بْنُ عُمَرَ ، قَالَ حَدَّثَنَا شُعْبَةُ ، عَنْ سُلَيْمَانَ ، قَالَ سَمِعْتُ زَيْدَ بْنَ وَهْبٍ ، قَالَ رَأَى حُذَيْفَةُ رَجُلاً لاَ يُتِمُّ الرُّكُوعَ وَالسُّجُودَ قَالَ مَا صَلَّيْتَ، وَلَوْ مُتَّ مُتَّ عَلَى غَيْرِ الْفِطْرَةِ الَّتِي فَطَرَ اللَّهُ مُحَمَّدًا صلى الله عليه وسلم.
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."