كتاب النكاح
16
The Book of Marriage
(5)
Chapter: The prohibition of marriage for one who is in Ihram, and it is disliked for him to propose marriage
(5)
باب تَحْرِيمِ نِكَاحِ الْمُحْرِمِ وَكَرَاهَةِ خِطْبَتِهِ ‏‏

Yazid b. al-Asamm reported:

Maimuna daughter of al-Harith narrated to me that Allah's Messenger (ﷺ) married her and he was not in the state of Ihram. And she (Maimuna) was my mother's sister and that of Ibn 'Abbas (Allah be pleased with them).
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا يَحْيَى بْنُ آدَمَ، حَدَّثَنَا جَرِيرُ بْنُ حَازِمٍ، حَدَّثَنَا أَبُو فَزَارَةَ، عَنْ يَزِيدَ بْنِ الأَصَمِّ، حَدَّثَتْنِي مَيْمُونَةُ بِنْتُ الْحَارِثِ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم تَزَوَّجَهَا وَهُوَ حَلاَلٌ قَالَ وَكَانَتْ خَالَتِي وَخَالَةَ ابْنِ عَبَّاسٍ ‏.‏
Reference : Sahih Muslim 1411
In-book reference : Book 16, Hadith 56
USC-MSA web (English) reference : Book 8, Hadith 3285
  (deprecated numbering scheme)