It was recorded by al-Bukhārī in "al-Adab al-Mufrad" (p. 129) through the chain of Muḥammad ibn ʿAmr from Abū Salamah from Abū Hurayrah as a marfūʿ ḥadīth. I said: And this is a good isnād.

"Cupping on an empty stomach is better, and it contains healing and blessing, and it increases intelligence and memory. So perform cupping with the blessing of Allāh on Thursday, and avoid cupping on Wednesday, Friday, Saturday, and Sunday as a precaution. Perform cupping on Monday and Tuesday, for it is the day when Allāh cured Ayyūb from his affliction and afflicted him on Wednesday, for no leprosy or vitiligo appears except on Wednesday or the night of Wednesday." It was recorded by Ibn Mājah (3487), Ibn ʿAdī (87/1), and al-Khaṭīb in "al-Faqīh wa-al-Mutafaqqih" (224/2) with its first part through the chain of ʿUthmān ibn Maṭar from al-Ḥasan ibn Abī Jaʿfar from Muḥammad ibn Juḥādah from Nāfiʿ from Ibn ʿUmar who said: "O Nāfiʿ, the blood has overwhelmed me, so seek a cupper for me, and make him gentle if you can, and do not make him an old man or a young boy, for I heard the Messenger of Allāh (ṣallá Allāhu ʿalayhi wa-sallam) say," and he mentioned it. Ibn ʿAdī said: "Perhaps the issue is from ʿUthmān ibn Maṭar, not from al-Ḥasan, for others narrate it from him." I said: And this al-Ḥasan is weak in ḥadīth despite his worship and virtue, as al-Ḥāfiẓ said in "al-Taqrīb." al-Dhahabī said in "al-Ḍuʿafāʾ": "A group declared him weak." And ʿUthmān ibn Maṭar is also weak. But al-Ḥasan has been corroborated as mentioned earlier by Ibn ʿAdī