Shama-il Tirmidhi Chapter 049, Hadith Number 003 (345).

Ibn 'Abbaas Radiyallahu 'Anhu said that Rasulullah Sallallahu 'Alayhi Wasallam took the treatment of cupping on both sides of his neck and between his shoulders, and paid the cupper his fees. If it had been haraam, he would not have paid it.

Commentary
As the blood has to be sucked out by the mouth, for this reason in some ahaadith this occupation and its income have been scorned, as has been mentioned previously. In some ahaadith its income has been declared undesirable and wicked. Due to this, some 'ulama say its fees are not permissible Imam Ahmad ibn Hambal has reconciled the two in this manner, that the prohibition is for free people and not for slaves. Since Abu Taybah Radiyallahu'Anhu was a slave, there remains no perplexity in paying a fee. Ibnul Jauzi says, it has been declared (a remuneration) wicked because, it is among the necessities of a Muslim, and to help another Muslim is waajib, therefore no remuneration should be taken, and this service should be rendered without a charge. The 'ulama have many views on this. Ibn 'Abbaas Radiyallahu 'Anhu has through this hadith proved its permissibility, and says if it was not permissible, Sayyidina Rasulullah Sallallahu'Alayhi Wasallam would not have paid a fee.