سنن النسائي

It was narrated that Abu Sa'eed Al-Khudri said: "The Messenger of Allah (ﷺ) 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 (ﷺ) used to pray. I looked at him when he had finished praying subh and his face was wet with water and mud."