It is narrated from Sayyiduna Shaddad bin Aws (may Allah be pleased with him); he said: The Prophet (peace and blessings be upon him) passed by a man who was being cupped on the eighteenth of Ramadan, and I was with him (peace and blessings be upon him). He (peace and blessings be upon him) said: "The one who cups and the one who is cupped have both broken their fast."
Hadith Referenceالمعجم الكبير للطبراني / باب الشين / 7094