It is narrated from Sa'id bin al-Musayyib (may Allah have mercy on him) that the Messenger of Allah (ﷺ) married Maymunah (may Allah be pleased with her) after coming out of the state of Ihram. Imam Shafi'i (may Allah have mercy on him) says that this issue is further strengthened by the decisions of 'Umar (may Allah be pleased with him) and Zaid bin Thabit (may Allah be pleased with him); both declared marriage in the state of Ihram to be invalid. And our master Abdullah bin 'Umar (may Allah be pleased with them both) said: "A Muhrim should neither marry nor propose."
Hadith Referenceالسنن المأثورة / باب ما جاء في فدية الأذى / 470
Hadith Takhrijسنن ابی داؤد، المناسک، باب المحرم یتزوج، رقم: 1845 وقال الالبانی: صحیح مقطوع۔