Mishkat al-Masabih 2086, 2087
Abu Sa'id al-Khudri said:
God’s messenger spent the first ten nights of Ramadan in devotion, and spent the middle ten nights in devotion in a round Turkish tent, after which he raised his head and said, “I have spent the first ten nights in devotion seeking this night, then I spent the middle ten nights in devotion, and after that I had a heavenly visitant and was told that it is in the last ten, so he who has engaged in devotion along with me should do so during the last ten nights, for I was shown this nights, then was caused to forget it, but I have seen myself prostrating in water and clay on the morning following, so seek it among the last ten and seek it in every night with an odd number.” He said: Rain fell that night, the mosque which was a thatched building dripped, and my eyes saw God’s messenger with traces of water and clay on his forehead on the morning after the twenty-first night. Bukhari and Muslim agree on the subject-matter, the wording being Muslim's up to “and was told it is it the last ten”, the remainder being Bukhari's. In the version of ‘Abdallah b. Unais he said it was the twenty-third night.

Muslim transmitted it.
وَعَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ رَضِيَ اللَّهُ عَنْهُمْ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ اعْتَكَفَ الْعَشْرَ الْأَوَّلَ مِنْ رَمَضَانَ ثُمَّ اعْتَكَفَ الْعَشْرَ الْأَوْسَطَ فِي قُبَّةٍ تُرْكِيَّةٍ ثُمَّ أَطْلَعَ رَأسه. فَقَالَ: «إِنِّي اعتكفت الْعشْر الأول ألتمس هَذِه اللَّيْلَة ثمَّ اعتكفت الْعَشْرَ الْأَوْسَطَ ثُمَّ أُتِيتُ فَقِيلَ لِي إِنَّهَا فِي الْعشْر الْأَوَاخِر فَمن اعْتَكَفْ مَعِي فَلْيَعْتَكِفِ الْعَشْرَ الْأَوَاخِرَ فَقَدْ أُرِيتُ هَذِهِ اللَّيْلَةَ ثُمَّ أُنْسِيتُهَا وَقَدْ رَأَيْتُنِي أَسْجُدُ فِي مَاءٍ وَطِينٍ مِنْ صَبِيحَتِهَا فَالْتَمِسُوهَا فِي الْعَشْرِ الْأَوَاخِرِ وَالْتَمِسُوهَا فِي كُلِّ وِتْرٍ» . قَالَ: فَمَطَرَتِ السَّمَاءُ تِلْكَ اللَّيْلَةَ وَكَانَ الْمَسْجِدُ عَلَى عَرِيشٍ فَوَكَفَ الْمَسْجِدُ فَبَصُرَتْ عَيْنَايَ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَعَلَى جَبْهَتِهِ أَثَرُ المَاء والطين وَالْمَاء مِنْ صَبِيحَةِ إِحْدَى وَعِشْرِينَ. مُتَّفَقٌ عَلَيْهِ فِي الْمَعْنَى وَاللَّفْظُ لِمُسْلِمٍ إِلَى قَوْلِهِ: 
" فَقِيلَ لِي: إِنَّهَا فِي الْعشْر الْأَوَاخِر ". وَالْبَاقِي للْبُخَارِيّ
وَفِي رِوَايَةِ عَبْدِ اللَّهِ بْنِ أُنَيْسٍ قَالَ: «لَيْلَة ثَلَاث وَعشْرين» . رَوَاهُ مُسلم