مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3433
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that Ibn ‘Abbas (رضي الله عنه) said: The Prophet (ﷺ) was treated with cupping by a slave belonging to Banu Bayadah, and the Prophet (ﷺ) gave him his fee. If it were haram, he would not have given it to him. And he told his masters to reduce some of the share of his earnings (that they took).
Musnad Ahmad 3457lts isnad is saheeh, al-Bukhari (2103) and Muslim (1202)]