ʿAlī, ʿUrwah ibn al-Zubayr, and Saʿīd ibn Jubayr.
Imām Aḥmad, however, held that cupping does break the fast. In the Musnad and in Sunan al-Tirmidhī it is related from Rāfiʿ ibn Khadīj that the Prophet ﷺ said, “The cupper and the one cupped have broken their fast.” Aḥmad and al-Bukhārī both declared this to be the most authentic report on the issue.
Abū Dāwūd likewise transmits—on the authority of Thawbān—that the Prophet ﷺ said, “The cupper and the one cupped have broken their fast.” Imām Aḥmad remarked, “The hadiths that state, ‘The cupper and the one cupped have broken their fast’ strengthen one another, and I follow them.”
Al-Ṭaḥāwī and others observed that these reports are mass-transmitted, reaching us through numerous Companions.
Shaykh al-Islām Ibn Taymiyyah said: “The narrations on this subject are many and have been scrutinized by the leading ḥadith authorities. Holding that cupping invalidates the fast is the view of most jurist-traditionists, such as Aḥmad, Isḥāq, Ibn Khuzaymah, and Ibn al-Munḏir, and it accords with sound analogy. Those who considered the fasting person’s cupping to be permissible argue from what al-Bukhārī recorded (1836): ‘The Prophet ﷺ underwent cupping while he was fasting and in a state of iḥrām.’”
Yet Aḥmad and others criticized the additional phrase “while he was fasting,” insisting that the authentic wording is simply, “He underwent cupping while he was in a state of iḥrām.” Aḥmad said, “The phrase ‘while he was fasting’ is an error on the part of Qabīṣah.”
Shaykh al-Islām added, “What Aḥmad has mentioned is exactly what the two Shaykhs—al-Bukhārī and Muslim—are agreed upon.”
The hadiths that state the fast is broken are explicit, sound, and come through multiple chains: fourteen individuals narrated them from the Prophet ﷺ, and Imām Aḥmad cited every one of their reports. How, then, could we prefer over them narrations that are either authentic but irrelevant, or relevant yet not authentic?
The correct ruling, therefore, is that cupping, fasd (venesection), incision, and any medical procedure that removes a large quantity of blood all nullify the fast, for the same physiological and legal rationale that applies to cupping applies equally to these practices.