Sunan an-Nasa'i, Book 13, Hadith 178 (In-Book) ⓘ
It was narrated that Abu Sa'eed Al-Khudri said: "The Messenger of Allah used to observe I'tikaf during the middle ten days of the month, and after the twentieth (day of the month), he would come out on the twenty-first and go back to his home, and those who were observing I'tikaf with him would go back like him. Then he stayed one month on the night when he used to go back home, and he addressed the people and enjoined upon them whatever Allah (SWT) willed. Then he said: 'I used to observe I'tikaf during these ten days, then I decided to spend the last ten days in I'tikaf. So whoever was observing I'tikaf with me, let him stay in his place of I'tikaf, for I was shown this night (Lailatul Qadr), then I was caused to forget it, so seek it during the last ten nights on the odd-numbered nights. And I saw myself prostrating in water and mud.'" Abu Sa'eed said: "It rained on the night of the twenty-first, and the roof of the Masjid leaked over the place where the Messenger of Allah used to pray. I looked at him when he had finished praying subh and his face was wet with water and mud."
أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا بَكْرٌ، - وَهُوَ ابْنُ مُضَرَ - عَنِ ابْنِ الْهَادِ، عَنْ مُحَمَّدِ بْنِ إِبْرَاهِيمَ، عَنْ أَبِي سَلَمَةَ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ، قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يُجَاوِرُ فِي الْعَشْرِ الَّذِي فِي وَسَطِ الشَّهْرِ فَإِذَا كَانَ مِنْ حِينِ يَمْضِي عِشْرُونَ لَيْلَةً وَيَسْتَقْبِلُ إِحْدَى وَعِشْرِينَ يَرْجِعُ إِلَى مَسْكَنِهِ وَيَرْجِعُ مَنْ كَانَ يُجَاوِرُ مَعَهُ ثُمَّ إِنَّهُ أَقَامَ فِي شَهْرٍ جَاوَرَ فِيهِ تِلْكَ اللَّيْلَةَ الَّتِي كَانَ يَرْجِعُ فِيهَا فَخَطَبَ النَّاسَ فَأَمَرَهُمْ بِمَا شَاءَ اللَّهُ ثُمَّ قَالَ " إِنِّي كُنْتُ أُجَاوِرُ هَذِهِ الْعَشْرَ ثُمَّ بَدَا لِي أَنْ أُجَاوِرَ هَذِهِ الْعَشْرَ الأَوَاخِرَ فَمَنْ كَانَ اعْتَكَفَ مَعِي فَلْيَثْبُتْ فِي مُعْتَكَفِهِ وَقَدْ رَأَيْتُ هَذِهِ اللَّيْلَةَ فَأُنْسِيتُهَا فَالْتَمِسُوهَا فِي الْعَشْرِ الأَوَاخِرِ فِي كُلِّ وَتْرٍ وَقَدْ رَأَيْتُنِي أَسْجُدُ فِي مَاءٍ وَطِينٍ " . قَالَ أَبُو سَعِيدٍ مُطِرْنَا لَيْلَةَ إِحْدَى وَعِشْرِينَ فَوَكَفَ الْمَسْجِدُ فِي مُصَلَّى رَسُولِ اللَّهِ صلى الله عليه وسلم فَنَظَرْتُ إِلَيْهِ وَقَدِ انْصَرَفَ مِنْ صَلاَةِ الصُّبْحِ وَوَجْهُهُ مُبْتَلٌّ طِينًا وَمَاءً .
also referenced under: Hadith 1356 (Reference) & Volume 2, Book 13, Hadith 1357 (DarusSalam)