Musannaf Ibn Abi Shayba 26:545

Waki' narrated to us, he said: 'Abd al-'Aziz narrated to us, from 'Abd Allah ibn Mawhab, he said: I heard Tamim al-Dari saying: I said, "O Messenger of Allah, what is the Sunnah regarding a man from the People of the Book who accepts Islam at the hands of a man from the Muslims?" He said: "He is the person most entitled to his life and his death."