عن ابي عمرو الشيباني أن رجلاً تنصر بعد إسلامه فأتي به علي فجعل يعرض عليه فقال ما أدري ما يقول غير أنه شهد أن المسيح إبن الله فوثب إليه علي فوطئه وأمر الناس أن يطؤوه ثم قال كُفوا فكفوا عنه وقد مات
معرفة السنن والأثار للبيهقي كتاب المرتد المكره على الردة
Abu ‘Amr Al-Shaybani related that a certain man became a Christian after having been in Islam, and he was brought to ‘Ali, who asked to be told about him. And the person said: The only thing I know he said was that he bears witness that the Messiah is the son of Allah. Then ‘Ali rushed on him and trampled him, and ordered the people to trample him. Then he said: That’s enough! So they stopped, since he was already dead.
Al-Bayhaqi, Ma’rifa Al-sunan wa Al-athar [Knowledge of the Sunnah and the Hadith], The book of apostates, Section: those forced to apostatize