The Prophet ﷺ said, "The cupper and the one being cupped have broken their fast."Shayban said, Abu Qilaba informed me that Abu Asma ar-Rahabi narrated to him that Thawban, the freed slave of the Messenger of Allah ﷺ, told him that he heard the Prophet ﷺ say this. Ahmad bin Hanbal narrated it to us.
حدثنا مسدد حدثنا يحيى عن هشام ح و حدثنا أحمد بن حنبل حدثنا حسن بن موسى حدثنا شيبان جميعا عن يحيى عن أبي قلابة عن أبي أسماء يعني الرحبي
عن النبي ﷺ قال أفطر الحاجم والمحجوم قال شيبان أخبرني أبو قلابة أن أبا أسماء الرحبي حدثه أن ثوبان مولى رسول الله ﷺ أخبره أنه سمع النبي ﷺ حدثنا أحمد بن حنبل
[Its chain of transmission is sahih] Ibn Majah narrated it in the Book of Fasting, chapter on what has been said regarding cupping for the fasting person, hadith no. 1680, from the hadith of Shayban, with this same wording. It is also found in Musnad Ahmad, 1/657, and Atraf Musnad, 5/283. Ibn Khuzayma graded it sahih, hadith nos. 1962 and 1963, as did Ibn Hibban, hadith no. 899, and Hakim, according to the standard of the two Shaykhs, 1/427, and Dhahabi agreed with him.