Musannaf Ibn Abi Shayba 36:318

Ubayd Allah ibn Musa narrated to us, from Musa ibn Ubaydah, who said: Iyas ibn Salamah narrated to me, from his father, who said: Quraysh sent Kharijah ibn Karz to scout them as a vanguard. He returned praising and speaking well of them. They said to him, "You are a Bedouin; they rattled their weapons at you, so your heart flew away, and you did not respond to what was said to you, nor did you say anything." Then they sent Urwah ibn Mas'ud. He came to him and said, "O Muhammad, what is this talk? You call to the Essence of Allah, then you have come to your people with the riffraff of the people—those you know and those you do not know—to sever their ties of kinship and to deem lawful their sanctity, their blood, and their wealth." He said, "I have not come to my people except to join their ties of kinship, and that Allah may replace for them a religion better than their religion, and livelihoods better than their livelihoods." He returned praising and speaking well of them. Iyas said, from his father: The affliction intensified upon those of the Muslims who were in the hands of the polytheists. He said: The Messenger of Allah (peace and blessings of Allah be upon him) called Umar and said, "O Umar, will you convey a message for me to your brothers among the Muslim captives?" He said, "Yes, O Prophet of Allah. By Allah, I have no clan in Makkah, and there is no clan more numerous than mine." Then he called Uthman and sent him to them. Uthman went out on his mount until he reached the camp of the polytheists. They rebuked him and spoke ill to him. Then Aban ibn Sa'id ibn al-As, his cousin, granted him protection and carried him on the saddle, riding behind him. When he arrived, he said, "O cousin, why do I see you humble?" He let down—and his lower garment was to the middle of his shins—and Uthman said to him, "This is the way of the lower garment of our companion." He did not leave anyone in Makkah among the Muslim captives without conveying to them what the Messenger of Allah (peace and blessings of Allah be upon him) had said. Salamah said: While we were resting at midday, the caller of the Messenger of Allah (peace and blessings of Allah be upon him) called out, "O people, the pledge! The pledge! The Holy Spirit has descended." He said: We rushed to the Messenger of Allah (peace and blessings of Allah be upon him) while he was under a Samurah tree, and we pledged allegiance to him. That is the saying of Allah: "Allah was certainly pleased with the believers when they pledged allegiance to you under the tree." He said: He pledged on behalf of Uthman, placing one of his hands upon the other. The people said, "Congratulations to Abu Abd Allah; he is circumambulating the House while we are here." The Messenger of Allah (peace and blessings of Allah be upon him) said, "Even if he were to stay for such and such a year, he would not circumambulate until I circumambulate."