Muwatta Malik, Book 20, Hadith 777 (In-Book)

Yahya related to me from Malik, from Nafi, that Abdullah ibn Umar used to say, "Someone in ihram may neither get married, nor arrange a marriage for himself or others."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يَقُولُ لاَ يَنْكِحِ الْمُحْرِمُ وَلاَ

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also referenced under: Book 20, Hadith 73 (USC-MSA)