Sayyiduna Shaddad bin Aws (may Allah be pleased with him) narrates: We were with the Messenger of Allah (peace and blessings be upon him) in the year of the Conquest of Makkah when he (peace and blessings be upon him) saw a man being cupped; eighteen days of Ramadan had passed. He (peace and blessings be upon him) was holding my hand, and he said: "The cupper and the cupped have broken their fast."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8300