The Quraysh were in a dither when they learned that the Prophet peace be and blessings upon him had pitched his camp so near to Makkah. But as the Prophet peace be and blessings upon him had no intention of fighting the Qurayshites, he thought it fit to send one of his companions to remove their apprehensions. He sent for Umar to depute him to Makkah, but Umar said, O Messenger of Allah peace be and blessings upon him, there is none of Bani Adiy b. Kab in Makkah who may protect me in case the Quraysh decided to lay hands on me.
Umar also suggested that,Uthman might be sent as his entire clan was there and he could very well deliver the message.
Uthman was then summoned by the Prophet peace be and blessings upon him and sent to the Quraysh to tell them that he had not come for war but merely for performing the Umrah.
The Prophet peace be and blessings upon him also asked Uthman to invite the Quraysh to Islam and to cheer the believing men and women still in Makkah with the glad tidings that God was about to make their religion victorious when they would not be required to conceal
(Zad al‐Ma'ad, Vol. I, p. 381)
LOVE PUT TO TRIAL
Uthman went to Makkah and delivered the message of the Prophet peace be and blessings upon him to Abu Sufyan and other leaders of the Quraysh. After the Makkans had heard the message brought by ‘Uthman they said. “If you want to go round the holy sanctuary, you may do so.” ‘Uthman, however, replied, “I won’t do so until the Prophet peace be and blessings upon him has gone round the K’aba”
(Ibn Hisham, Vol. II, p. 135)
later, after his return from Makkah, certain Muslims said to him, “Abu ‘Abdullah, you have been fortunate enough to fulfill your heart’s desire by going round the K’aba.” Don’t be unfair to me,’ replied ‘Uthman. “I declare by Him who holds my life that if I were detained there for a whole year and the Prophet peace be and blessings upon him were to remain in Hudaybiyah, I would not have gone round the K’aba until the Prophet peace be and blessings upon him had done so. Frankly speaking, the Quraysh did invite me to circumambulate the House of God, but I declined.”
(Zad al‐Ma’ad, Vol. I, p. 382).
THE PLEDGE OF RIDHWAN
In the meantime, the Prophet peace be and blessings upon him was informed that ‘Uthman had been killed. He summoned the people to
vow in avenging ‘Uthman’s death. Everybody gathered round the Prophet peace be and blessings upon him impatiently. Standing under the shade of a tree, the Prophet peace be and blessings upon him took one person at a time from the fourteen hundred standing around him to get their assurance. And after everyone had obliged to the oath, he struck one of his hands on the other, saying. “This is the pledge on behalf of ‘Uthman.”
(Zad al‐Ma’ad, Vol. p. 382)
Thus was the pledge of Ridhwan (the pledge that earned God's pleasure) taken under an Acacia tree. It is mentioned in the Qur'an:
“Allah was well pleased with believers when they swore allegiance unto thee beneath the tree, and He knew what was in their hearts, and He sent down peace of reassurance on them, and hath rewarded them with a near victory.”