TODAY IS THE FEAST of Saint Cyril of Jerusalem (ca. 315—386), Bishop and Doctor of the Church, who is known for a series of lectures given to catechumens during Lent, preparing them for Baptism — and later during the Easter Season about the mysteries of the Sacraments.
His catechetical lectures are here.
Saint Cyril speaks much of the heresies, and the heresy of Arianism was very active in his day; although he was on the orthodox side, his views — at the time of these lectures — were semi-Arian, but this was before the development of the Nicene Creed, which he accepted.
These lectures were of utmost importance in shaping the Church in the era following the Second Vatican Council. The Rite of Christian Initiation of Adults (RCIA) was explicitly modeled after these lectures, and it is from these that Communion in the hand is justified (although this practice is not seen anywhere else).
Despite problems, the parts I've read of the lectures are clear, delightful, and very rich in Catholic doctrine and practice. Saint Cyril presents his material clearly and logically.