Language:
كتاب الأذان
10  
Call to Prayers (Adhaan)
(119)
Chapter: Not performing bowing perfectly
(119)
باب إِذَا لَمْ يُتِمَّ الرُّكُوعَ
Sahih al-Bukhari 791

Narrated Zaid bin Wahb:

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."

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.‏
Reference : Sahih al-Bukhari 791
In-book reference : Book 10, Hadith 186
USC-MSA web (English) reference : Vol. 1, Book 12, Hadith 757
  (deprecated numbering scheme)