Musannaf Ibn Abi Shayba 26:410

Waki’ narrated to us, he said: Ja’far ibn Burqan narrated to us, from Maymun ibn Mihran, who said: Al-‘Urs ibn Qays al-Kindi sent for me and asked me about two Christian brothers, one of whom accepted Islam while the other died and left behind wealth. I said: Mu’awiyah used to say, "If he were a Christian, he would have inherited from him, and Islam did not increase him [the Muslim brother] except in severity [i.e., restriction]." Al-‘Urs ibn Qays said: We know that, and ‘Umar ibn al-Khattab, regarding the paternal aunt of al-Ash’ath ibn Qays who died while she was a Jewess, did not allow him to inherit anything from her.