Anas bin Maalik Radiyallahu 'Anhu said:
"Rasulullah Sallallahu 'Alayhi Wasallam used the treatment of cupping on both sides of his mubaarak neck and between both shoulders, and generally took this treatment on the seventeenth, nineteenth or the twenty first of the (lunar) month".
English reference: Book 49, Hadith 347
Arabic reference: Book 50, Hadith 364