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

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 1165 d
In-book reference : Book 13, Hadith 270
USC-MSA web (English) reference : Book 6, Hadith 2620
  (deprecated numbering scheme)