Musnad Ahmad 3:3

Yahya ibn Sa'id narrated to us, from Malik, Nafi' narrated to me, from Nabih ibn Wahb, from Aban ibn 'Uthman, from his father, from the Prophet, peace and blessings of Allah be upon him, who said: "The one in the state of ihram shall not marry, nor shall he give in marriage, nor shall he propose."