It is narrated from Sayyiduna Uthman (may Allah be pleased with him) that he (peace and blessings be upon him) said: "The muhrim should neither contract his own marriage nor anyone else's, nor propose marriage."
It is also narrated from Ibn Umar (may Allah be pleased with them both) in the same way, but he did not attribute it to the Prophet (peace and blessings be upon him). It has also been narrated from Ibn Umar as marfu' (attributed to the Prophet), but what is correct from Ibn Umar is that it is mawquf (his own statement).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14200