كتاب الصيام
13  
The Book of Fasting
(40)
Chapter: The virtue of Lailat Al-Qadr and the Exhortation to seek it; When it is and the most likely times to seek it
(40)
باب فَضْلِ لَيْلَةِ الْقَدْرِ وَالْحَثِّ عَلَى طَلَبِهَا وَبَيَانِ مَحَلِّهَا وَأَرْجَى أَوْقَاتِ طَلَبِهَا
Sahih Muslim 1165 d

Salim b. 'Abdullah b. 'Umar reported that his father said:

I heard Allah's Messenger (ﷺ) as saying: So far as Lailat-ul-Qadr is concerned. some persons among you have seen it (in a dream) in the first week and some persons among you have been shown that it is in the last week; so seek it in the last ten (nights).
وَحَدَّثَنِي حَرْمَلَةُ بْنُ يَحْيَى، أَخْبَرَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي يُونُسُ، عَنِ ابْنِ شِهَابٍ، أَخْبَرَنِي سَالِمُ بْنُ عَبْدِ اللَّهِ بْنِ عُمَرَ، أَنَّ أَبَاهُ، - رضى الله عنه - قَالَ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ لِلَيْلَةِ الْقَدْرِ ‏ "‏ إِنَّ نَاسًا مِنْكُمْ قَدْ أُرُوا أَنَّهَا فِي السَّبْعِ الأُوَلِ وَأُرِيَ نَاسٌ مِنْكُمْ أَنَّهَا فِي السَّبْعِ الْغَوَابِرِ فَالْتَمِسُوهَا فِي الْعَشْرِ الْغَوَابِرِ ‏"‏ ‏.‏
Reference : Sahih Muslim 1165d
In-book reference : Book 13, Hadith 270
USC-MSA web (English) reference : Book 6, Hadith 2620
  (deprecated numbering scheme)