(7) Fasting
كتاب الصوم
(4a) Chapter: Keeping the Fast free from Imperfection - Section 1
(3) باب تنزيه الصوم - الفصل الأول
Mishkat al-Masabih 2002 
Ibn ‘Abbas said that the Prophet had himself cupped when he was wearing the ihram and also when he was fasting. (Bukhari and Muslim.)
وَعَنِ ابْنِ عَبَّاسٍ قَالَ: إِنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ احْتَجَمَ وَهُوَ مُحْرِمٌ وَاحْتَجَمَ وَهُوَ صَائِمٌ
 مُتَّفَقٌ عَلَيْهِ  (الألباني)حكم :
Reference : Mishkat al-Masabih 2002
In-book reference : Book 7, Hadith 46