Shaddad bin Aws (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) came to a man at al-Baqi' who was being cupped, while he was holding my hand. Eighteen nights of Ramadan had passed. He (peace and blessings be upon him) said: "The cupper (hajim) and the cupped (mahjum) have both broken their fast."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8282