Musannaf Ibn Abi Shayba 28:222

'Abd al-Rahim ibn Sulayman narrated to us, from Hajjaj, from Sa'id ibn Abi Burdah, from his father, from Abu Musa, who said: The Messenger of Allah (may Allah bless him and grant him peace) sent me and Mu'adh to Yemen. He said: Then he came to me one day while I had with me a Jew who had been a Muslim, but had reverted from Islam to Judaism. He said: "I will not dismount until you strike his neck." Hajjaj said: And Qatadah narrated to me that Abu Musa had been inviting him for forty days.