Mishkat al-Masabih 23 Medicine and Spells كتاب الطب والرقى 35

وَعَنْ أَبِي هُرَيْرَةَ عَنْ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «مَنِ احْتَجَمَ لِسَبْعَ عَشْرَةَ وَتِسْعَ عَشْرَةَ وَإِحْدَى وَعِشْرِينَ كَانَ شِفَاءً لَهُ مِنْ كُلِّ دَاء» . رَوَاهُ أَبُو دَاوُد

Abu Huraira reported God’s messenger as saying, “If anyone has himself cupped on the 17th, 19th, and 21st, it will be a remedy for every disease.” Abu Dawud transmitted it.