Sayyiduna Shaddad bin Aws (may Allah be pleased with him) narrates: I passed by with the Messenger of Allah (peace and blessings be upon him) when eighteen nights of Ramadan had passed. He (peace and blessings be upon him) saw a man who was being cupped, and he (peace and blessings be upon him) said: "The one who cups and the one who has been cupped (the hajim and the mahjum) have broken their fast."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8283