Sayyiduna Tamim al-Dari (may Allah be pleased with him) says: I asked the Messenger of Allah (peace and blessings be upon him): if a disbeliever becomes Muslim at the hands of a Muslim, what is the practice concerning him? The Messenger of Allah (peace and blessings be upon him) said: "He has more right than all people over his life and his death."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الولاء / 21458