The day of Bu'ath was a day (i.e. battle) which Allah caused to take place just before the mission of His Apostle so that when Allah's Messenger (ﷺ) came to Medina, they (the tribes) had divided (into hostile groups) and their nobles had been killed; and all that facilitated their conversion to Islam.
Sahih al-Bukhari Book 63, Hadith 155
← Previous Hadith An Ansari woman who gave the pledge of allegiance to the Prophet (ﷺ) that the Ansar drew lots concerning the dwelling of the Emigrants. `Uthman bin Maz'un was decided to dwell with them (i.e. Um Al-`Ala's family), `Uthman fell ill and I nursed him till he died, and we covered him with his clothes. Then the Prophet (ﷺ) came to us and I (addressing the dead body) said, "O Abu As-Sa'ib, may Allah's Mercy be on you! I bear witness that Allah has honored you." On that the Prophet (ﷺ) said, "How do you know that Allah has honored him?" I replied, "I do not know. May my father and my mother be sacrificed for you, O Allah's Messenger (ﷺ)! But who else is worthy of it (if not `Uthman)?" He said, "As to him, by Allah, death has overtaken him, and I hope the best for him. By Allah, though I am the Apostle of Allah, yet I do not know what Allah will do to me," By Allah, I will never assert the piety of anyone after him. That made me sad, and when I slept I saw in a dream a flowing stream for `Uthman bin Maz'un. I went to Allah's Messenger (ﷺ) and told him of it. He remarked, "That symbolizes his (good) deeds."

Sahih al-Bukhari Book 63, Hadith 154 Next Hadith → That once Abu Bakr came to her on the day of `Id-ul-Fitr or `Id ul Adha while the Prophet (ﷺ) was with her and there were two girl singers with her, singing songs of the Ansar about the day of Buath. Abu Bakr said twice. "Musical instrument of Satan!" But the Prophet (ﷺ) said, "Leave them Abu Bakr, for every nation has an `Id (i.e. festival) and this day is our `Id."

Sahih al-Bukhari Book 63, Hadith 156