Sayyiduna Abu Musa (may Allah be pleased with him) said: I came to the Prophet (peace and blessings be upon him) with two men of the Ash'aris (and he mentioned the hadith, until he said:) So he sent him over Yemen, then sent Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) after him. When he reached him, he laid out a cushion for him and said: Dismount. There was a man with him who was bound. He asked: What is this? He said: This man was a Jew who accepted Islam, then went back to his religion, the evil religion, and became a Jew. He said: I will not sit until he is killed; this is the judgement of Allah and His Messenger (peace and blessings be upon him). He said: Yes, sit down. He said three times: I will not sit until he is killed; this is the judgement of Allah and His Messenger. So he gave the order concerning him, and he was killed.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المرتد / 16881