Musannaf Ibn Abi Shayba 26:550

Ibn Idris narrated to us, from Layth, from Abu al-Ash'ath, from his master, who said: I asked Umar about a man who embraced Islam at my hands. He said: "You are the most entitled of people to his inheritance, as long as he does not leave behind an heir. If he does not leave behind an heir, then it is for the public treasury (Bayt al-Mal)."