عَنِ ابْنِ عَبَّاسٍ ـ رضى الله عنهما ـ قَالَ احْتَجَمَ النَّبِيُّ صلى الله عليه وسلم وَأَعْطَى الْحَجَّامَ أَجْرَهُ، وَلَوْ عَلِمَ كَرَاهِيَةً لَمْ يُعْطِهِ.
Narrated on the authority of Ibn `Abbas that:
When the Prophet (ﷺ) was cupped, he paid the man who cupped him his wages. If he had known it to be disliked (i.e makrooh) he would not have paid him.
Reported by al-Bukhaari.
As for the Prophet sallahu alayhi wa salam describing the earnings of the cupper to be khabith, then that doesn’t imply it to be impermissible. Rather, it shows that it is from the low class earnings which is belittled. A similar usage for the word khabith is used in the following ayah:
ولا تيمموا الخبيث منه تنفقون ولستم بآخذيه إلا أن تغمضوا فيه
“And do not aim at that which is khabith (i.e low class of earnings and properties) in order to give in charity, (though) you would not take it [yourself] except with your eyes closed”
AbdulFattaah Bin Uthman