The Messenger of Allah ﷺ had himself cupped when he was fasting. Abu Dawud said: Wuhaib b. Khalid narrated a similar tradition from Ayyub through a different chain of narrators. Ja'far b. Rabi'ah and Hisham, that is, Ibn Hassan, narrated a similar tradition from 'Ikrimah on the authority of Ibn 'Abbas.  

أَنَّ رَسُولَ اللَّهِ ﷺ احْتَجَمَ وَهُوَ صَائِمٌ  

The Messenger of Allah ﷺ had himself cupped when he was fasting and wearing ihram (pilgrim garb).  

أَنَّ رَسُولَ اللَّهِ ﷺ احْتَجَمَ وَهُوَ صَائِمٌ مُحْرِمٌ  

A man from the Companions of the Prophet ﷺ told me that the Messenger of Allah ﷺ prohibited cupping and perpetual fasting, but he had not made them unlawful showing mercy on his Companions. Thereupon he was asked: Messenger of Allah, you observe perpetual fast till dawn. He replied: I observe perpetual fast till dawn (for) my Lord gives me food and drink.  

حَدَّثَنِي رَجُلٌ مِنْ أَصْحَابِ النَّبِيِّ ﷺ أَنَّ رَسُولَ اللَّهِ ﷺ نَهَى عَنِ الْحِجَامَةِ وَالْمُوَاصَلَةِ وَلَمْ يُحَرِّمْهُمَا إِبْقَاءً عَلَى أَصْحَابِهِ فَقِيلَ لَهُ يَا رَسُولَ اللَّهِ إِنَّكَ تُوَاصِلُ إِلَى السَّحَرِ فَقَالَ إِنِّي أُوَاصِلُ إِلَى السَّحَرِ وَرَبِّي يُطْعِمُنِي وَيَسْقِينِي  

We would not allow a man who was fasting to get himself cupped due to abomination of hardship.  

أَنَسٌ مَا كُنَّا نَدَعُ الْحِجَامَةَ لِلصَّائِمِ إِلاَّ كَرَاهِيَةَ الْجَهْدِ