Ibn Hibban

Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) narrates: The Prophet Muhammad (peace and blessings be upon him) used to observe i'tikaf during the middle ten days of Ramadan. When twenty nights had passed and the twenty-first night arrived, he did not return to his residence; whoever had observed i'tikaf with him went back. The Prophet (peace and blessings be upon him) stayed in the month in which he used to observe i'tikaf, until the night came in which he would return. Then he addressed the people and commanded them with whatever Allah willed, then he said: I used to observe i'tikaf in this ten (days), then it seemed appropriate to me that I should also observe i'tikaf in the last ten (days), and whoever has observed i'tikaf with me should remain in his place of i'tikaf. I was shown this night, but then I was made to forget it, but you should seek it in the odd nights of the last ten (days). I saw myself prostrating in water and mud during this night. Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) narrates: We saw on the twenty-first night that water began to drip from the place of prayer of the Prophet (peace and blessings be upon him) in the mosque. I saw the Prophet (peace and blessings be upon him), when he finished the morning prayer, there was water and mud on his blessed face.