Mishkat al-Masabih 4542
Abu Kabsha al-Anmari told that God’s messenger used to have himself cupped on the top of his head and between his shoulders and that he used to say:
“If anyone pours out any of this blood he will not suffer if he applies no medical treatment for anything.” 

Abu Dawud and Ibn Majah transmitted it.
وَعَن أبي كَبْشَة الْأَنْمَارِيِّ: أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ كَانَ يحتجم على هامته وَبَين كفيه وَهُوَ يَقُولُ: «مَنْ أَهْرَاقَ مِنْ هَذِهِ الدِّمَاءِ فَلَا يَضُرُّهُ أَنْ لَا يَتَدَاوَى بِشَيْءٍ لِشَيْءٍ» . رَوَاهُ أَبُو دَاوُد وَابْن مَاجَه