Sunnah.com reference : Book 8, Hadith 28English translation : Book 8, Hadith 999Arabic reference : Book 8, Hadith 992
Narrated 'Uthman (RA):
Allah's Messneger (ﷺ) said: "One who is in Ihram may not marry, or be given in marriage."

[Reported by Muslim]. In another narration by him it says: "He should not ask someone's hand in marriage."
وَعَنْ عُثْمَانَ ‏- رضى الله عنه ‏- قَالَ : قَالَ رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-{ لَا يَنْكِحُ اَلْمُحْرِمُ , وَلَا يُنْكَحُ }  رَوَاهُ مُسْلِمٌ .‏ وَفِي رِوَايَةٍ لَهُ : { وَلَا يَخْطُبُ }   1‏ .‏‏1 ‏- تقدم برقم ( 733 )‏.‏