Sahih Muslim Book - 4, Hadith - 1066

حَدَّثَنَا مُحْرِزُ بْنُ عَوْنِ بْنِ أَبِى عَوْنٍ حَدَّثَنَا خَلَفُ بْنُ خَلِيفَةَ الأَشْجَعِىُّ أَبُو أَحْمَدَ عَنِ الْوَلِيدِ بْنِ سَرِيعٍ مَوْلَى آلِ عَمْرِو بْنِ حُرَيْثٍ عَنْ عَمْرِو بْنِ حُرَيْثٍ قَالَ صَلَّيْتُ خَلْفَ النَّبِىِّ -صلى الله عليه وسلم- الْفَجْرَ فَسَمِعْتُهُ يَقْرَأُ (فَلاَ أُقْسِمُ بِالْخُنَّسِ الْجَوَارِ الْكُنَّسِ) وَكَانَ لاَ يَحْنِى رَجُلٌ مِنَّا ظَهْرَهُ حَتَّى يَسْتَتِمَّ سَاجِدًا.

It was narrated that 'Amr bin Huraith said: "I offered Fajr prayers behind the Prophet (s.a.w) and I heard him reciting: "So verily, I swear by the planets that recede (i.e. disappear during the day and appear during the night). And by the planets that move swiftly and hide themselves". And no man among us would bend his back until he had prostrated fully."