Some of what has reached us from the hadith masters on authenticating this hadith

Ali bin Sa'id al-Nasawi (may Allah have mercy on him) narrates: I heard Imam Ahmad bin Hanbal (may Allah have mercy on him) being asked: Which hadith is most authentic in your view concerning the breaking of the fast of "the cupper and the cupped"? He said: The hadith of Thawban (may Allah be pleased with him), through the narration of Yahya bin Abi Kathir (may Allah have mercy on him), from Abu Qilabah, from Abu Asma', from Thawban. It was said to Imam Ahmad bin Hanbal (may Allah have mercy on him): Then what about the hadith of Rafi' bin Khadij (may Allah be pleased with him)? He said: Ma'mar (may Allah have mercy on him) is alone in narrating it.

Ali bin Abdullah (Ibn al-Madini, may Allah have mercy on him) said: I do not know of any hadith on the breaking of the fast of "the cupper and the cupped" more authentic than this one, meaning the hadith of Rafi' bin Khadij (may Allah be pleased with him).

Uthman bin Sa'id al-Darimi (may Allah have mercy on him) said: In my view, the hadith of "the cupper and the cupped" has been established as authentic on account of the hadith of Thawban and Shaddad (may Allah be pleased with them both), and I hold this view. And I heard Ahmad bin Hanbal hold this view and mention that the hadith of Thawban and Shaddad was authentic in his view.

Ahmad bin Hanbal (may Allah have mercy on him) said: The hadiths on the breaking of the fast of the "hajim" and the "mahjum" (the cupper and the cupped), and the hadith "There is no marriage without a guardian", are hadiths that strengthen one another, and I adopt them.

Ishaq bin Ibrahim (may Allah have mercy on him) said about the hadith of Shaddad bin Aws (may Allah be pleased with him): This is a sahih (authentic) chain by which the proof is established, and this hadith is sahih through several chains, and we hold it.

Ali bin al-Madini (may Allah have mercy on him) said: The hadith of Shaddad bin Aws (may Allah be pleased with him) from the Messenger of Allah (peace and blessings be upon him), that he (peace and blessings be upon him) saw a man being cupped in Ramadan, was narrated by Asim al-Ahwal from Abu Qilabah, from Abu al-Ash'ath, from Shaddad; and Yahya bin Abi Kathir narrated it from Abu Qilabah, from Abu Asma', from Thawban. In my view both hadiths are sahih (authentic), since it is possible that he (Abu Qilabah) heard it from both of them.

Abu Dawud (may Allah have mercy on him) said: I said to Imam Ahmad bin Hanbal (may Allah have mercy on him): Which hadith of "The cupper and the cupped have broken their fast" is most authentic? He said: The hadith of Ibn Jurayj (may Allah have mercy on him), which he narrated through Makhul (may Allah have mercy on him) from Thawban (may Allah be pleased with him).

Abu Ali al-Hafiz (may Allah have mercy on him) said: I said to Abdan al-Ahwazi: Is it authentic that the Prophet (peace and blessings be upon him) was cupped while fasting? He said: I heard Abbas al-Anbari (may Allah have mercy on him) say: I heard Ali bin al-Madini (may Allah have mercy on him) say: The hadith of Abu Rafi' from Abu Musa (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said, "The cupper and the cupped have both broken their fast", is authentic.
And it reached me from Abu Isa al-Tirmidhi that he said: I asked Abu Zur'ah about the hadith of Ata' from Abu Hurayrah in marfu' form, and he said: It is a hasan (good) hadith.