Imam al-Bukhari (may Allah have mercy on him) said: Ayyash told me; (he said:) Abd al-A'la narrated to us, from Yunus, from al-Hasan, from more than one (of the Companions), in a marfu' form (attributed to the Prophet); he said: "The cupper and the one cupped have both broken their fast."
He was asked: Is this from the Prophet (peace and blessings be upon him)? He said: "Yes." Then he said: "Allah knows best."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / Q8275