We know that the apostle John was exiled for his faith late in life (Revelation 1:9). The Bible does not give us details on how the apostle John died, but tradition gives us a few theories.
The most plausible theory of John’s death states that John was arrested in Ephesus and faced martyrdom when his enemies threw him in a huge basin of boiling oil. However, according to the tradition, John was miraculously delivered from death. The authorities then sentenced John to slave labor in the mines of Patmos. On this island in the southern part of the Aegean Sea, John had a vision of Jesus Christ and wrote the prophetic book of Revelation. The apostle John was later freed, possibly due to old age, and he returned to what is now Turkey. He died as an old man sometime after AD 98, the only apostle to die peacefully.
Another theory concerning John’s death is associated with a second-century bishop named Papias of Hierapolis. According to one commentary on Papias’s writings, John was killed by a group of Jewish men. However, many historians believe Papias was misquoted or misread and doubt the credibility of this theory.
There is also a legend that says John did not die but rather ascended straight to heaven like Enoch and Elijah. There is no biblical evidence to lend validity to this story.
Ultimately, it is not essential to know how the apostle John died. What is important is the fact that he was not ashamed of Christ (see Luke 9:26) and was willing to die for his faith. A man will not die for something he knows to be a lie. John knew the truth that Jesus had been resurrected, and he was willing to die rather than to renounce his faith in his Savior.