Towards the close of the year 625, the Holy Prophet married Hafsa, and Uthman was married to Umm Kulthum the third daughter of the Holy Prophet. While still a child she was engaged to Utaibah a son of Abu Lahb, an uncle of the Holy Prophet. When the Holy Prophet declared his mission, Abu Lahb opposed him, and under his instructions his son Utaibah repudiated his engagement to Umm Kulthum.

When the Holy Prophet married Umm Kulthum to Uthman, he said to her, "Verily, your husband resembles most among men your forefather Abraham, and your father Muhammad". Ibn Asakir has recorded on the authority of lbn Umar that the Holy Prophet said," I find a resemblance in Uthman to my forefather Abraham".

Uthman's union with Umm Kulthum was as happy as that of the union between Uthman and Ruqayya. Unfortunately such happiness was short lived, and Umm Kulthum died in 630 barely six years after her marriage. Umm Kulthum bore no child. Ruqayya left a son Abdullah, but he died two years after the death of his mother.

After the death of Umm Kulthum; Uthman once again became a victim of despair and disconsolation. Touched by the sadness of Uthman, the Holy Prophet asked the people:

"Give your daughters in marriage to Uthman. If I had a third daughter, I would assuredly give her in marriage to him. I have never wedded any daughter to him save under inspiration."

Ibn Asakir records on the authority of Ali that the Holy Prophet said to Uthman: "If I had forty daughters, I would have wedded them with you one after the other, until no one of them was left".

Thereafter Uthman married a number of wives, but the memories of his union with Ruqayya and Umm Kulthum always remained fresh in his mind. He felt sorry that he could not enjoy the company of the daughters of the Holy Prophet for long, and he had been deprived of the honor of being the son-in-law of the Holy Prophet.