Musannaf Ibn Abi Shaybah 34934 — What they said on a man who accepts

Mukhariq (may Allah have mercy on him) said that Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) sent Muhammad bin Abi Bakr as governor over the people of Egypt. He wrote to Sayyiduna Ali (may Allah be pleased with him) asking about the zanadiqah (heretics), some of whom worshipped the sun and moon, some worshipped other things, and some claimed Islam. Sayyiduna Ali (may Allah be pleased with him) wrote to him and ordered him regarding the zanadiqah to kill whoever claimed Islam, and to leave all the rest to worship whatever they wished.