Saint Theristus was born to a Calabrian woman in Palermo, then the Emirte of Sicily. His mother had been recently captured from a Saracen raid on the coast of Calabria - his father, Arcone di Cursano had been killed during the raid. Growing up as a Christian in a Islamic territory was extremely difficult but he kept strong to his faith. When he was 14, his mother convinced him to flee and go back to Calabria, their home country. He did so and crossed the Straight of Messina miraculously in a boat that had no sails or oars and, believing him to be a Moor, was taken by the townspeople to the Bishop. At the Bishop's feet he asked that he could be baptized.
As he continued to get older and wiser, he began feeling pulled more and more to the monks around Stylus and eventually joined as a young adult. Within just a few years he was elected to Abbot of the monastery. As abbot, he discovered a hidden inheritance and treasure left behind at his family's farm from his deceased father - following in the rule of Saint Basil he had the inheritance sold and distributed to the poor.
A legend tells that one June he travelled to see a knight who provided food for the monks through his estates. When he arrived at the fields of Marone and Maturavolo, he offered the farmers bread and wine he had carried with him but a terrible storm suddenly came upon them. The farmers panicked, knowing this storm could completely destroy the harvest. Saint Theristus though, dropped to his knees and began to pray, telling the farmers to quickly harvest the wheat as he prayed. Miraculously the storm was constantly delayed while he prayed, allowing the farmers to fully harvest their fields. This event and other very similar miracles with farmers earned him the nickname of Theristis (Reaper or Harvester).
Saint John Theristus died at his monastery of natural causes in 1129 AD. A story tells that King Roger had suffered a terrible wound on his face that was miraculously healed when Saint John Theristus's tunic was placed on his face. King Roger II, in thanksgiving, founded the monastery in Nemore and named it Saint John after the saint. In 1160, Pope Alexander VIII moved Saint Theristus's body to Stylus and had them placed with the relics of Saint Ambrose and Nicholas in a church built by the Minims Fathers. The church was then embellished with marble works by the Redemptorists in 1791. Today, in the center of the cloister, stands an ancient well with four columns, covered by a canopy with a praying child holding a cross inside of a tin ship - this is in memory of Saint John Theristus's miraculous journey by sea.
Saint John Theristus's feast day is celebrated on February 23rd. Notably, he is considered a Saint by both the Catholic and Orthodox church despite his death occurring almost a century after the Great Schism. The Orthodox church celebrates his feast day on the same day.