Upvote:1
Who was the first person on record who was killed by a Christian or group of Christians for religious disagreements?
Undoubtedly the answer to this question would seem to be lost to history. Nevertheless we can go back into the first few centuries of Christianity for a glimmer of evidence to make an answer.
The first person who was murdered by some Christian or group of Christians for religious disagreements, may be a detail now lost to history.
Andrew Stephenson describes late antiquity as "one of the darkest periods in the history of Christianity" characterizing as mingling the evils of "worldly ambition, false philosophy, sectarian violence and riotous living." Constantine initially persecuted the Arians but eventually ceased the persecution and declared himself a convert to their theology. Sectarian violence became more frequent and more intense during the reign of Constantius II (7 August 317 β 3 November 361). When Paul, the orthodox bishop of Constantinople, was banished by imperial decree, a riot broke out that resulted in 3000 deaths. Paul was deposed five times before finally being strangled by imperial decree. Monks in Alexandria were the first to gain a reputation for violence and cruelty. Although less frequent than in Antioch and Constantinople, sectarian disturbances also racked Antioch. At Ephesus, a fight broke out in a council of bishops resulting in one of them being murdered. Gibbon's assessment was that "the bonds of civil society were torn asunder by the fury of religious factions." Gregory of Nazianzus (c. 329 β 25 January 390) lamented that the Kingdom of heaven had been converted into the "image of hell" by religious discord. - Sectarian violence among Christians
Upvote:2
Your question starts with a couple of assumptions that don't hold up. First, the earliest Christians had plenty of heated disagreements, starting with doctrinal conflicts over the extent to which the Law of Moses was binding (or not) on Gentile believers. Chapter 15 of Acts, and the whole of Paul's letter to the church at Galatia, record those issues. Second, even at the peak of the Inquisitions, only a very small percentage of accused heretics were sentenced to death.
(Please note, I bring these up not to justify anything -- even one killing by the church for heresy was one too many. I just want to correct some common misconceptions, ones that I used to share until I dug more deeply into the facts.)
That said, the specific you're seeking, THE first person to die for heresy, may be a detail lost to history. Based on my own very limited research, the earliest major, fatal action against a heretical movement was the persecution of the Donatists during the time of Augustine: Donatism.
It seems there were strong political factors involved, not merely the suppression of a heresy. And according to the article, even though Augustine argued that the use of force was justified, he later protested the extremes that the Roman authorities were going to.
So to sum it up, TL;DR style: the use of violence against heresy seems to have come about in conjunction with the church becoming a political force rather than a strictly spiritual organization.