This mission of teaching that belonged to the apostles and their first fellow workers was continued by the Church. Making herself day after day a disciple of the Lord, she earned the title of “Mother and Teacher.”1 From Clement of Rome to Origen,2 the post-apostolic age saw the birth of remarkable works. Next we see a striking fact: Some of the most impressive Bishops and pastors, especially in the third and fourth centuries considered it an important part of their espiscopal ministry to deliver catechetical instructions and write treatises. It was the age of Cyril of Jerusalem and John Chrysostom, of Ambrose and Augustine, the age that saw the flowering, from the pen of numerous Fathers of the Church, of works that are still models for us.
It would be impossible here to recall, even very briefly the catechesis that gave support to the spread and advance of the Church in the various periods of history, in every continent, and in the widest variety of social and cultural contexts. There was indeed no lack of difficulties. But the word of the Lord completed its course down the centuries; it sped on and triumphed, to use the words of the Apostle Paul.3
Cf. MM (AAS 53 [1961], p. 401): the Church is “mother” because by baptism she unceasingly begets new children and increases God’s family; she is “teacher” because she makes her children grow in the grace of their baptism by nourishing their sensus fidei through instruction in the truths of faith.
Cf., for example the letter of Clement of Rome to the Church of Corinth, the Didache, the Epistola Apostolorum, the writings of Irenaeus of Lyons (Demonstratio Apostolicae Praedicationis and Adversus Haereses), of Tertullian (De Baptismo), of Clement of Alexandria (Paedagogus), of Cyprian (Testimonia ad Quirinum), of Origen (Contra Celsum), etc.
Cf. 2 Thes. 3:1.