We may wonder how both the sons of Zebedee, James and John, came to drink from the chalice of martyrdom, since Scripture tells us only that the apostle James was decapitated by Herod. John, on the other hand, died a natural death. But in the history of the Church we are told that he was to be martyred in a vat of boiling oil; an athlete of Christ, he was saved from the oil and banished to the island of Patmos. John too suffered martyrdom; he, like the three young men who stood in the burning fire, drank from the chalice of martyrdom, though his persecutor failed to spill his blood.
--St. Jerome,
Commentary on Matthew, 20, 23.
