Sahih Muslim Book 8, Hadith Number 3279.

Chapter: Mubrim (one who is in the state of Ihram) is forbidden to marry and the disapproval of giving the proposal (in this state).

Nubaih b. Wahb reported: Umar b. Ubaidullah b. Ma’mar sent me to Aban b. Uthman as he wanted to make the proposal of the marriage of his son with the daughter of Shaiba b. Uthman. He (Aban b. Uthman) was at that time (busy) in the season of Pilgrimage. He said: I deem him to be a man of the desert (for it is a common thing) that a Muhrim can neither marry, nor is he allowed to be married to anyone. It is Uthman (b. Affan) who reported this to us from Allah’s Messenger (May peace be upon him).