Sahih Muslim , Book 6, Hadith 214 (In-Book) ⓘ

Ubayy b Ka'b reported: By Allah, I know about Lailat-ul Qadr and I know it fully well that it is the twenty-seventh night (during Ramadan) on which the Messenger of Allah commanded us to observe prayer. (Shu'ba was in doubt about these words:" the night on which the Messenger of Allah [may peace be upon him] commanded us to observe the prayer." This has been transmitted to me by a friend of mine.)

حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، قَالَ سَمِعْتُ عَبْدَةَ بْنَ أَبِي لُبَابَةَ، يُحَدِّثُ عَنْ زِرِّ بْنِ حُبَيْشٍ، عَنْ أُبَىِّ بْنِ كَعْبٍ، قَالَ أُبَىٌّ فِي لَيْلَةِ الْقَدْرِ وَاللَّهِ إِنِّي لأَعْلَمُهَا وَأَكْثَرُ عِلْمِي هِيَ اللَّيْلَةُ الَّتِي أَمَرَنَا رَسُولُ اللَّهِ صلى الله عليه وسلم بِقِيَامِهَا هِيَ لَيْلَةُ سَبْعٍ وَعِشْرِينَ - وَإِنَّمَا شَكَّ شُعْبَةُ فِي هَذَا الْحَرْفِ - هِيَ اللَّيْلَةُ الَّتِي أَمَرَنَا بِهَا رَسُولُ اللَّهِ صلى الله عليه وسلم ‏.‏ قَالَ وَحَدَّثَنِي بِهَا صَاحِبٌ لِي عَنْهُ ‏.‏