Sahih Al Bukhari (677)

أم العلاء امرأة من نسائهم قد بايعت النبي (صلى الله عليه وسلم) أخبرته "أن عثمان بن مظعون طار له سهمه في السكنى حين أقرعت الأنصار سكنى المهاجرين قالت أم العلاء فسكن عندنا عثمان بن مظعون فاشتكى فمرضناه حتى إذا توفي وجعلناه في ثيابه دخل علينا رسول الله (صلى الله عليه وسلم) فقلت رحمة الله عليك أبا السائب فشهادتي عليك لقد أكرمك الله فقال لي النبي (صلى الله عليه وسلم) وما يدريك أن الله أكرمه فقلت لا أدري بأبي أنت وأمي يا رسول الله فقال رسول الله (صلى الله عليه وسلم) أما عثمان فقد جاءه والله اليقين وإني لأرجو له الخير والله ما أدري وأنا رسول الله ما يفعل به قالت فوالله لا أزكي أحدا بعده أبدا وأحزنني ذلك قالت فنمت فأريت لعثمان عينا تجري فجئت إلى رسول الله (صلى الله عليه وسلم) فأخبرته فقال ذاك عمله"

Um Al-‘Ala narrated: That when the Ansar drew lots as to which of the emigrants should dwell with which of the Ansar, the name of ‘Uthman ibn Maz‘un came out (to be in their lot). Um Al-‘Ala further said: "‘Uthman stayed with us, and we nursed him when he got sick, but he died. We shrouded him in his clothes, and Allah's Messenger (peace be upon him) came to our house and I said, (addressing the dead 'Uthman), 'O Abu As-Sa'ib! May Allah be merciful to you. I testify that Allah has blessed you.' The Prophet (peace be upon him) said to me: "How do you know that Allah has blessed him?" I replied: 'I do not know O Allah's Messenger! May my parents be sacrificed for you.' Allah's Messenger (peace be upon him) said, 'As regards ‘Uthman, by Allah he has died and I really wish him every good, yet, by Allah, although I am Allah's Messenger, I do not know what will be done to him.' Um Al-‘Ala added, 'By Allah I shall never attest the piety of anybody after him. And what Allah's Messenger (peace be upon him) said made me sad." Um Al-‘Ala further said: "Once I slept and saw in a dream, a flowing stream for ‘Uthman. So I went to Allah's Messenger (peace be upon him) and told him about it, he said, 'That is (the symbol of) his deeds."