Muwatta Imam Malik Book of General Subjects, Hadith 28

Malik related to me from Ibn Shihab from Ibn Muhayyisa al-Ansari, one of the Banu Haritha, that he asked permission from the Messenger of Allah ﷺ to give payment for cupping, and he forbade him to do it. He continued to ask and seek his permission until he said, "Feed the ones who drive your water-carrying camels," meaning "your slaves."

وَحَدَّثَنِي مَالِكٌ، عَنِ ابْنِ شِهَابٍ، عَنِ ابْنِ مُحَيِّصَةَ الأَنْصَارِيِّ، أَحَدِ بَنِي حَارِثَةَ أَنَّهُ اسْتَأْذَنَ رَسُولَ اللَّهِ ﷺ فِي إِجَارَةِ الْحَجَّامِ فَنَهَاهُ عَنْهَا فَلَمْ يَزَلْ يَسْأَلُهُ وَيَسْتَأْذِنُهُ حَتَّى قَالَ " اعْلِفْهُ نُضَّاحَكَ " . يَعْنِي رَقِيقَكَ .