Shahzad Masih, a cleaner at a hospital near the eastern city of Gujrat, was arrested on 13th July after his co-worker accused him of insulting Islam's prophet Muhammad, which is a crime punishable by death in Pakistan.
The accused's father told World Watch Monitor that the argument related to who Christians worship.
Shafaqat Masih said: "My son told him that we follow Jesus and then their discussion became sour, at which point a doctor intervened and calmed them down."
The police complaint was lodged by another man, Nadeem Ahmed, who claims to have called Shahzad from his mobile phone repair shop, near the Shameem Riaz Polyclinic to ask him about what he'd said. In his report, Ahmed states that the teenager repeated his "abusive words" against Muhammad before fleeing.
Shafaqat Masih told World Watch Monitor, which reports the story of Christians around the world under pressure for their faith, that two days before the complaint was lodged, his son's colleague, Ishtiaq Jalali, told his son that Christians worship at the shrines of Muslim sages.
He said: "My son told him that he didn't know about this and he would ask me about it."
The police chief, Shahbaz Hinjra, told a local newspaper that Masih was in their custody and that they were investigating the matter.
Former Punjab parliamentarian Tahir Naveed Chaudhry, leader of the largest Christian political party, told World Watch Monitor that he had personally investigated the matter and found that the initial argument had centred over Masih's colleague's attempts to convert him to Islam.
He said: "When our people try to defend themselves and their faith then often it becomes an issue and later such cases are lodged."
Pakistan is overwhelmingly Muslim but after Hindus, Christians are the second-largest minority group with estimates ranging from two to 10 million for Christians, and 2.5 to 4.5 million for Hindus.
Several blasphemy cases have been registered before in Gujrat, one of the most conservative areas of the Punjab province. In August 2015, 15 Christians were accused of blasphemy after they used the word "apostle" to describe a pastor who had died years before. Then in July 2016, a Christian man was accused of blasphemy after a religious argument on messaging service WhatsApp.
Both cases are still pending in court.
