Bulugh al-Maram, Book 6, Hadith 756 (English)

Ibn 'Abbas (RAA) narrated, ‘The Messenger of Allah had himself cupped while he was in the state of Ihram Agreed upon.

وَعَنِ اِبْنِ عَبَّاسٍ رَضِيَ اَللَّهُ عَنْهُمَا; أَنَّ اَلنَّبِيَّ ‏- صلى الله عليه وسلم ‏-{ اِحْتَجَمَ وَهُوَ مُحْرِمٌ } مُتَّفَقٌ عَلَيْهِ 1‏.‏ ‏1 ‏- صحيح.‏ رواه البخاري ( 1835 )‏، ومسلم ( 1202 )‏.‏

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also referenced under: Book 6, Hadith 30 (In-Book)