Sahih al-Bukhari 6644
Sahih al-Bukhari · Book 83: Oaths and Vows · How did the oaths of the Prophet (saws) use to be?
Narrated Anas bin Malik:
حَدَّثَنِي إِسْحَاقُ ، أَخْبَرَنَا حَبَّانُ ، حَدَّثَنَا هَمَّامٌ ، حَدَّثَنَا قَتَادَةُ ، حَدَّثَنَا أَنَسُ بْنُ مَالِكٍ ـ رضى الله عنه ـ أَنَّهُ سَمِعَ النَّبِيَّ صلى الله عليه وسلم يَقُولُ " أَتِمُّوا الرُّكُوعَ وَالسُّجُودَ، فَوَالَّذِي نَفْسِي بِيَدِهِ إِنِّي لأَرَاكُمْ مِنْ بَعْدِ ظَهْرِي إِذَا مَا رَكَعْتُمْ وَإِذَا مَا سَجَدْتُمْ " .
I heard the Prophet (ﷺ) saying, "Perform the bowing and the prostration properly (with peace of mind), for, by Him in Whose Hand my soul is, I see you from behind my back when you bow and when you prostrate."