Musannaf Ibn Abi Shaybah 34933 — What they said on a man who accepts

Ibn Ubayd bin al-Abras (may Allah have mercy on him) said that a man who had been a Christian, then accepted Islam, then became a Christian again was brought to Sayyiduna Ali bin Abi Talib (may Allah be pleased with him). Sayyiduna Umar (may Allah be pleased with him) asked him about this matter, and he told him (may Allah be pleased with him). Then Sayyiduna Ali (may Allah be pleased with him) stood up towards him and kicked him with his foot. Then the people also stood up and beat him until they killed him.