Yahya related to me from Malik from Yazid ibn Abdullah ibn al- Hadi from Muhammad ibn Ibrahim al-Harith at-Taymi from Abu Salama ibn Abd ar-Rahman that Abu Said al-Khudri said, "The Messenger of Allah, may Allah bless him and grant him peace, used to do itikaf in the middle ten days of Ramadan. One year he was doing itikaf and then, when it came to the night of the twenty-first, which was the night before the morning when he would normally have finished his itikaf, he said, 'Whoever has done i'tikaf with me should continue doing itikaf for the last ten days. I saw a certain night and then I was made to forget it. I saw myself prostrating the following morning in water and clay. Look for it in the last ten days, and look for it on the odd days.' "

Abu Said continued, "The sky poured with rain that night and the mosque had a roof (made of palm fronds) and the mosque was soaked. With my own eyes I saw the Messenger of Allah, may Allah bless him and grant him peace, leave with traces of water and clay on his forehead and nose, in the morning after the night of the twenty- first."

حَدَّثَنِي زِيَادٌ، عَنْ مَالِكٍ، عَنْ يَزِيدَ بْنِ عَبْدِ اللَّهِ بْنِ الْهَادِ، عَنْ مُحَمَّدِ بْنِ إِبْرَاهِيمَ بْنِ الْحَارِثِ التَّيْمِيِّ، عَنْ أَبِي سَلَمَةَ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ، أَنَّهُ قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يَعْتَكِفُ الْعَشْرَ الْوُسُطَ مِنْ رَمَضَانَ فَاعْتَكَفَ عَامًا حَتَّى إِذَا كَانَ لَيْلَةَ إِحْدَى وَعِشْرِينَ وَهِيَ اللَّيْلَةُ الَّتِي يَخْرُجُ فِيهَا مِنْ صُبْحِهَا مِنَ اعْتِكَافِهِ قَالَ ‏ "‏ مَنِ اعْتَكَفَ مَعِي فَلْيَعْتَكِفِ الْعَشْرَ الأَوَاخِرَ وَقَدْ رَأَيْتُ هَذِهِ اللَّيْلَةَ ثُمَّ أُنْسِيتُهَا وَقَدْ رَأَيْتُنِي أَسْجُدُ مِنْ صُبْحِهَا فِي مَاءٍ وَطِينٍ فَالْتَمِسُوهَا فِي الْعَشْرِ الأَوَاخِرِ وَالْتَمِسُوهَا فِي كُلِّ وِتْرٍ ‏"‏ ‏.‏ قَالَ أَبُو سَعِيدٍ فَأُمْطِرَتِ السَّمَاءُ تِلْكَ اللَّيْلَةَ وَكَانَ الْمَسْجِدُ عَلَى عَرِيشٍ فَوَكَفَ الْمَسْجِدُ - قَالَ أَبُو سَعِيدٍ - فَأَبْصَرَتْ عَيْنَاىَ رَسُولَ اللَّهِ صلى الله عليه وسلم انْصَرَفَ وَعَلَى جَبْهَتِهِ وَأَنْفِهِ أَثَرُ الْمَاءِ وَالطِّينِ مِنْ صُبْحِ لَيْلَةِ إِحْدَى وَعِشْرِينَ ‏.‏
USC-MSA web (English) reference : Book 19, Hadith 10
Arabic reference : Book 19, Hadith 700