The Messenger of Allah ﷺ said, "Whoever is cupped on the seventeenth, the nineteenth, or the twenty-first, it will be a cure for every disease."
قال رسول الله ﷺ: من احتجم لسبع عشرة، وتسع عشرة، وإحدى وعشرين، كان شفاء من كل داء.
It was narrated by Abu Dawud (3861), and Hakim graded it sahih (4/210), both from the hadith of Abu Tuba Rabi bin Nafi, who said, "Saeed bin Abdul-Rahman Jumahi told us, from Suhayl bin Abu Salih, from his father, from Abu Hurairah," and he mentioned it. The wording is that of Abu Dawud, and Hakim confined himself to mentioning the seventeenth. Its isnad is hasan because of Saeed bin Abdul-Rahman Jumahi, for he is hasan al-hadith, except that Saji said, "He narrates hadiths from Hisham and Suhayl that are not corroborated." I have not found anyone who said that besides Saji. Hakim said, "This is a hadith sahih according to the criterion of Muslim."Something with a similar meaning was narrated from Ibn Abbas, from the Prophet ﷺ, who said, "The best day on which to have cupping done is the seventeenth, the nineteenth, and the twenty-first," and he said, "I did not pass by any gathering of angels on the night I was taken on the night journey without them saying, 'Take to cupping, Muhammad.'" It was narrated by Ahmad (3316) - and the wording is his - Tirmidhi (2053), Ibn Majah (3477), and Hakim (4/209, 409), all of them by way of Abbad bin Mansur, from Ikrima, from Ibn Abbas, and he mentioned it.Tirmidhi said, "Hasan gharib, we do not know it except from the hadith of Abbad bin Mansur." Hakim said, "Sahih in isnad." I say, in it is Abbad bin Mansur, who is daif by the agreement of the scholars, and he practiced tadlis in this hadith in addition to his weakness, as was explained previously in the discussion of the night journey. As for the statement of Hafiz in Fath al-Bari (10/150), "The hadith of Ibn Abbas as recorded by Ahmad and Tirmidhi has narrators who are trustworthy, but it is defective," this is not as he said, for Abbad bin Mansur is not among the trustworthy narrators.