Saint Cyril was a Bishop and confessor and is a Doctor of the Church.
Saint Cyril was likely born in 313 AD near Caesarea (the area is modern day Israel), but it is known with certainity exactly what year he was born. We do know that he was ordained a deacon in 335 by Saint Bishop Macarius of Jerusalem after being raised reading the writings of the early Christian theologians. Eight years after being ordained a deacon, Saint Cyril was ordained a priest by Saint Bishop Maximus, successor of Saint Macarius.
Saint Cyril succeeded Saint Maximus as the Bishop of Jerusalem around 350 AD. Relations between Saint Cyril (now bishop) and Acacius of Caesarea (Bishop of Caesarea) quickly became very strained. Acacius was a staunch defender of Arianism and accused Saint Cyril early on of selling church property for personal gain. At the time of accusation, Jerusalem was facing a terrible famine and the church historians Sozomen and Theodoret wrote that Saint Cyril sold a robe given to him by Constantine. A church council that was held in 357 under Acacius (in which Saint Cyril had not been invited) deposed Saint Cyril, forcing him to take refuge with the Bishop of Tarsus, Silvanus. Only a year later though, in early 359, the Council of Seleucia reinstated Saint Cyril and deposed Acacius. Any hope for stability was quickly dashed when Constantius reversed the decision in 360, forcing Saint Cyril into exile.
In 361, Emperor Julian allowed him to return, but this return lasted only until 367 when the new Arian Emperor Valens banished him. Eleven years later, in 378, Emperor Gratian paved the way for him to return and the First Council of Constantinople expressly confirmed his position as the Bishop of Jerusalem. It was at this same council that he voted for acceptance of the term homoousios (that declared God the Father and God the same being in essence - literally homos, same, and ousia, being/essence).
Saint Cyril's most famous surviving work is a collection of 23 lectures given to candidates for Baptism. The first eighteen lectures are known as the Catechetical Lectures while the final five are often referred to as the Mystagogic Catecheses. The first set, based on the baptismal creed of Jerusalem were given during Lent and the other set given after Easter to the newly baptized. A famous lecture is the 13th Lecture, which deals with the Crucifixion and burial of Jesus Christ. In this lecture, Saint Cyril makes clear his belief that Jesus went to his death with both full knowledge and willingness, maintaining his faith and forgiving those involved with the event, writing:
“who did not sin, neither was deceit found in his mouth, who, when he was reviled, did not revile, when he suffered did not threaten”
Of the Blessed Sacrament, Saint Cyril is clear:
"Since He Himself has declared and said of the bread: This is My Body, who shall dare to doubt any more? And when He asserts and says: This is My Blood, who shall ever hesitate and say it is not His Blood?"
"Do not think it mere bread and wine, for it is the Body and Blood of Christ, according to the Lord's declaration". "Having learned this and being assured of it, that appears to be bread is not bread, though perceived by the taste, but the Body of Christ, and what appears to be wine is not wine, though the taste says so, but the Blood of Christ . . . strengthen thy heart, partaking of it as spiritual (food), and rejoice the face of thy soul"
Saint Cyril was declared a Doctor of the Church in 1883. His feast day is celebrated on March 18th.