Musnad Ahmad 33:872

Muhammad ibn Ubayd narrated to us, al-A’mash narrated to us, from Abu Sufyan, from Jabir, who said: "Ubayy ibn Ka’b fell ill with an illness, so the Prophet, peace and blessings of Allah be upon him, sent a physician to him, and he cauterized him on his ak-hal (the median vein of the arm)."