Kharijah bin Zayd bin Thabit (may Allah be pleased with him) says that Umm al-Ala (may Allah be pleased with her) had given the pledge of allegiance to the Prophet (peace and blessings be upon him). She says: When the Ansar drew lots for the housing of the Muhajirun, the housing of Sayyiduna Uthman bin Maz'un (may Allah be pleased with him) fell to our share. He fell ill and died, and we shrouded him in his clothes. Then the Messenger of Allah (peace and blessings be upon him) came to us, and I said: "May the mercy of Allah be upon you, O Abu al-Sa'ib! I bear witness that Allah has honoured you." The Prophet (peace and blessings be upon him) said: "How do you know?" She says: By Allah, O Messenger of Allah (peace and blessings be upon him), I do not know. He (peace and blessings be upon him) said: "As for him, the certainty (death) has come to him, and I hope for good for him from Allah. By Allah, though I am the Messenger of Allah, I do not know what will be done with me or with you." I said: By Allah, I will never again declare anyone pure. She says: I saw for Sayyiduna Uthman bin Maz'un (may Allah be pleased with him) in a dream a flowing spring. I mentioned it to the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) said: "That is his deeds, which continue to flow for him."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العتق / 21412