Musnad Abu Ya'la al-Mawsili 109:289

Narrated to us Ibn Numayr, narrated to us Abu Mu'awiyah, from al-A'mash, from Abu Sufyan, from Jabir, who said: The Messenger of Allah (may Allah bless him and grant him peace) cauterized Ubayy ibn Ka'b for a vein, and he cauterized him on his *akhal* (the median cubital vein).