The Messenger of Allah ﷺ used to spend the middle ten days of Ramadan in retirement and devotion (i'tikaf) in the mosque. One year he had retirement and devotion in the mosque (as usual); when the twenty-first night came, and this night when he used to come out his devotion in the mosque, he said: He who has engaged himself in devotion along with me should do so during the last ten days; I saw that night, that was caused to forget it, but I have seen myself prostrating in water and mud on the morning following (that night), so seek it in the last ten days and seek it every night with an odd number. Abu sa'id said: Rain fell that night, the mosque that was thatched building dripped, and my eyes saw the Messenger of Allah ﷺ with the traces of water and mud, on his forehead on the morning following the twenty-first night. (Using translation from Abū Dāʾūd 1382)  

كَانَ رَسُولُ اللهِ ﷺ «يَعْتَكِفُ فِي الْعَشْرِ الْوَسَطِ مِنْ رَمَضَانَ فَاعْتَكَفَ عَامًا حَتَّى إِذَا كَانَ لَيْلَةَ إِحْدَى وَعِشْرُونَ وَهِيَ اللَّيْلَةُ الَّتِي يَخْرُجُ مِنْ صَبِيحَتِهَا مِنِ اعْتِكَافِهِ» قَالَ «مَنْ كَانَ اعْتَكَفَ مَعِي فَلْيَعْتَكِفْ الْعَشْرَ الْأَوَاخِرَ فَأُرِيتُ هَذِهِ اللَّيْلَةَ ثُمَّ أُنْسِيتُهَا وَقَدْ رَأَيْتُنِي أَسْجُدُ مِنْ صَبِيحَتِهَا فِي مَاءٍ وَطِينٍ فَالْتَمِسُوهَا فِي الْعَشْرِ الْأَوَاخِرِ وَالْتَمِسُوهَا فِي كُلِّ وِتْرٍ» قَالَ أَبُو سَعِيدٍ فَأَمْطَرَتِ السَّمَاءُ تِلْكَ اللَّيْلَةَ وَكَانَ الْمَسْجِدُ عَلَى عَرِيشٍ فَوَكَفَ الْمَسْجِدُ قَالَ أَبُو سَعِيدٍ فَبَصُرَتْ عَيْنَايَ رَسُولَ اللهِ ﷺ عَلَى جَبِينِهِ وَأَنْفِهِ أَثَرُ الْمَاءِ وَالطِّينِ مِنْ صَبِيحَةِ لَيْلَةِ إِحْدَى وَعِشْرِينَ  

I asked Abu Saʿid, and he was a friend of mine, (about the Night of Qadr) and he said, "We practiced Iʿtikaf (seclusion in the mosque) in the middle third of the month of Ramadan with the Prophet ﷺ . In the morning of the 20th of Ramadan, the Prophet ﷺ came and addressed us and said, 'I was informed of (the date of the Night of Qadr) but I was caused to forget it; so search for it in the odd nights of the last ten nights of the month of Ramadan. (In the dream) I saw myself prostrating in mud and water (as a sign). So, whoever was in Iʿtikaf with me should return to it with me (for another 10-day's period)', and we returned. At that time there was no sign of clouds in the sky but suddenly a cloud came and it rained till rainwater started leaking through the roof of the mosque which was made of date-palm leaf stalks. Then the prayer was established and I saw Messenger of Allah ﷺ prostrating in mud and water and I saw the traces of mud on his forehead." (Using translation from Bukhārī 2016)   

تَذَاكَرْنَا لَيْلَةَ الْقَدْرِ فِي نَفَرٍ مِنْ قُرَيْشٍ فَأَتَيْتُ أَبَا سَعِيدٍ الْخُدْرِيَّ وَكَانَ صَدِيقًا لِي فَقُلْتُ أَلَا تَخْرُجُ بِنَا إِلَى النَّخْلِ فَخَرَجَ وَعَلَيْهِ خَمِيصَةٌ فَقُلْتُ سَمِعْتَ رَسُولَ اللهِ ﷺ يَذْكُرُ لَيْلَةَ الْقَدْرِ؟ قَالَ نَعَمْ اعْتَكَفْنَا مَعَ رَسُولِ اللهِ ﷺ فِي الْعَشْرِ الْأَوْسَطِ مِنْ رَمَضَانَ فَخَرَجْنَا صَبِيحَةَ عِشْرِينَ فَخَطَبَ رَسُولُ اللهِ ﷺ فَقَالَ «إِنِّي رَأَيْتُ لَيْلَةَ الْقَدْرِ وَإِنِّي أُنْسِيتُهَا وَهِيَ فِي الْعَشْرِ الْأَوَاخِرِ فِي وِتْرٍ وَإِنِّي رَأَيْتُ أَنِّي أَسْجُدُ فِي مَاءٍ وَطِينٍ وَمَنْ كَانَ اعْتَكَفَ مَعَ رَسُولِ اللهِ ﷺ فَلْيَرْجِعْ» فَجَاءَتْ سَحَابَةٌ فَمُطِرْنَا حَتَّى سَالَ سَقْفُ الْمَسْجِدِ وَكَانَ مِنْ جَرِيدِ النَّخْلِ وَأُقِيمَتِ الصَّلَاةُ وَكَانَ رَسُولُ اللهِ ﷺ يَسْجُدُ فِي الْمَاءِ وَالطِّينِ حَتَّى رَأَيْتُ أَثَرَ الطِّينِ فِي جَبْهَتِهِ