In 631 C.E. the Muslims from Madina proceeded to Makkah to perform the Hajj. The Holy Prophet stayed at Madina, and the pilgrims were led by Abu Bakr as "Amir ul Hajj". Uthman accompanied the caravan.
On the occasion of the Hajj, a proclamation was made to the effect that henceforward non-Muslims were not to be allowed to visit the Kaaba or perform the pilgrimage. No one was to circumambulate the Kaaba naked. Polytheism was banned. Where the Muslims had any agreements with the polytheists such agreements were to be honored. Where there was no agreement, the polytheists were allowed a grace period of four months after which polytheism was not to be tolerated. That made Arabia the land of Islam.
After the Hajj, Uthman stayed at Makkah for some time. He married at Makkah Umm Saeed Fatima b Al Walid b Abd Shams, a Quraish lady. Thereafter Uthman returned to Madina with his bride.
"When a person dies, his works end, except for three: ongoing charity, knowledge that is benefited from, and a righteous child who prays for him."
Prophet Mohammed (PBUH)
"The best of what a man leaves behind are three: a righteous child who supplicates for him, ongoing charity the reward of which reaches him, and knowledge that is acted upon after him."
Sunan Ibn Mājah
"Every day two angels come down from Heaven and one of them says, 'O Allah! Compensate every person who spends in Your Cause,' and the other (angel) says, 'O Allah! Destroy every miser.'"
Sahih Bukhari