Sunnah.com reference : Book 7, Hadith 161English translation : Book 7, Hadith 915Arabic reference : Book 7, Hadith 909
Narrated Ibn 'Abbas (RA):
Allah's Messenger (ﷺ) had himself cupped and gave the one who cupped him his pay; and if it were prohibited he would not have given him (his pay).

[Reported by al-Bukhari].
وَعَنْ اِبْنِ عَبَّاسٍ ‏-رَضِيَ اَللَّهُ عَنْهُمَا‏-; أَنَّهُ قَالَ: { اِحْتَجَمَ رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-وَأَعْطَى اَلَّذِي حَجَمَهُ أَجْرَهُ }  وَلَوْ كَانَ حَرَاماً لَمْ يُعْطِهِ.‏ رَوَاهُ اَلْبُخَارِيُّ  1‏ .‏‏1 ‏- صحيح.‏ رواه البخاري ( 2103 )‏.‏