Jami` at-Tirmidhi Book 49, Hadith 95
"When 'Uthman was besieged, he looked out over them from atop his house and said: 'I remind you by Allah. Do you know that when (mount) Hira shook, the Messenger of Allah (ﷺ) said: "Be firm O Hira! For there is none upon you except a Prophet, a Siddiq, and a martyr?"' They said: 'Yes.' He said: 'I remind you by Allah! Do you know that the Messenger of Allah (ﷺ) said, about the army of distress (Al-'Usrah): "Who will spend something which shall be accepted (by Allah)?" And the people were struggling during difficult times, so I prepared that army?' They said: 'Yes.' Then he said: 'I remind you by Allah. Do you know that no one drank from the well of Rumah but have to pay for it, then I bought it and made it for the rich, the poor, and the wayfarer?' They said: 'O Allah! Yes!'" And he listed other things. This Hadith is Hasan Sahih Gharib from this route; as a narration of Abu 'Abdur-Rahman As-Sulami from 'Uthman.
that the Messenger of Allah (ﷺ) said: "For every Prophet there is a friend (Rafiq), and my friend" - meaning in Paradise - "is 'Uthman."
"I witnessed the Prophet (ﷺ) while he was exhorting support for the 'army of distress.' 'Uthman bin 'Affan stood and said: 'O Messenger of Allah! I will take the responsibility of one-hundred camels, including their saddles and water-skins, in the path of Allah.' Then he I will take the responsibility of three-hundred camels, including their saddles and water-skins, in the path of Allah.' So I saw the Messenger of Allah (ﷺ) descend from the Minbar while he was saying: 'It does not matter what 'Uthman does after this, it does not matter what 'Uthman does after this.'"