Cyril was bishop of Jerusalem during the four turbulent decades after Constantine had built the Anastasis (the Holy Sepulchre church) over the tomb of Christ. He was exiled three times by Arianising emperors and Arian-sympathising local synods, spending in total sixteen years in exile.
His enduring achievement is the twenty-four Catechetical Lectures he delivered to the catechumens preparing for baptism at the Easter Vigil — eighteen pre-baptismal instructions, and five Mystagogical Catecheses delivered to the newly baptised during Easter Week, explaining the rites of Baptism, Chrismation (Confirmation), and the Eucharist they had just received. These are the earliest detailed Christian explanations of the sacraments we possess.
He attended the First Council of Constantinople (381), which completed the Nicene Creed, and died at Jerusalem in 386. Leo XIII declared him a Doctor of the Church in 1882.