"That the Prophet to you.' Abu Musa gave him a cushion to sit down, then a man was brought who had been a Jew, then he became a Muslim, then he reverted to Kufr. Mu'adh said: 'I will not sit down until he is killed; this is the decree of Allah and His Messenger,' (saying it) three times. When he was killed, he sat down."

Sunan an-Nasa'i Book 37, Hadith 101