وَعَنِ ابْنِ عَبَّاسٍ رَضِيَ اللَّهُ عَنْهُمَا
أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ كَانَ يَسْتَحِبُّ الْحِجَامَةَ لِسَبْعَ عَشْرَةَ وَتِسْعَ عَشْرَةَ وَإِحْدَى وَعِشْرِينَ
Ibn Abbas said the Prophet (sallallahu alayhi wa sallam) liked to have himself cupped on the 17th, 19th, and 21st. Baghawi transmitted it in Sharh as-sunna.
Mishkat al-Masabih 4354, Book 24, Medicine and Spells, Hadith 34. 1 min read