Hadith 14:63
Sahih (Al-Albani)
Narrated Anas:
We would not allow a man who was fasting to get himself cupped due to abomination of hardship.
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مَسْلَمَةَ، حَدَّثَنَا سُلَيْمَانُ، - يَعْنِي ابْنَ الْمُغِيرَةِ - عَنْ ثَابِتٍ، قَالَ قَالَ أَنَسٌ مَا كُنَّا نَدَعُ الْحِجَامَةَ لِلصَّائِمِ إِلاَّ كَرَاهِيَةَ الْجَهْدِ
Original Reference: Sunan Abi Dawud 2375