In his preface to the Popular Patristics publication of On the Incarnation, C.S. Lewis writes “It is a good rule, after reading a new book, never to allow yourself another new one till you have read an old one in-between. If that is too much for you, you should at least read one old one to every three new ones.”

New books are great, but they are untested—we don’t know which ones will stand the test of time. But old books have been sifted by time. It’s always good for us to look at the context of the people that came before us and see how the world looked from their time and place.

For Christians, it is even more important we recognize our heritage. Our beliefs are not composed out of thin air, but they come from the revelation of Jesus Christ and were handed down to His disciples through Scriptures and the Church, which is the “pillar and the foundation of the truth” (1 Timothy 3:15).

Here are four books which have not only stood the test of time, but had a great impact on the understanding of Christian doctrine to Christians living in the time shortly after Christ’s ascension, during the Church’s building period.

1. On the Incarnation, by Athanasius of Alexandria

Athanasius was a deacon in Alexandria during the Arian controversy in the fourth century. Arians denied the divinity of Jesus Christ, and Athanasius vehemently defended the doctrine of the Trinity from the growing Arian sect. He wrote On the Incarnation in defense of the full divinity and full humanity of Christ. This was subsequently what put him under fire when Athanasius stood against great persecution from the Arians throughout his life. He was exiled five times by four different Roman emperors for this position, but remained faithful to what he had written and taught.

Why you should read it:

In On the Incarnation, Athanasius argues the eternal nature of the Trinity and affirms that Jesus Christ is not a creation of God the Father, but existed from the very beginning. He does so with fairly simple language, using the scriptures as a guide. It’s a quick read that tells of the redeeming work that came through the God-man, Jesus Christ in a more complete way. I found it to be an excellent primer for orthodox Christian doctrine on the incarnation of Jesus Christ.

2. Confessions, by Augustine of Hippo

Confessions is the autobiography of Augustine. He retells of his Christian upbringing by his mother, his sinful and wayward youth and his conversion from the Manichaen cult to Christianity. Augustine also provides many spiritual insights and meditations into his story. Confessions is considered the first Christian biographical work and influenced many writers for years to come.

Why you should read it:

Augustine is considered one of the—if not the single most—influential theologians of the Church. His works inspired Christian writers, thinkers and theologians for centuries afterwards. He’s been hailed as a “doctor” of the Church and a scholar of scholars among Christians. If you want to begin to know which people Thomas Aquinas, Martin Luther or John Calvin looked up to as spiritual guides, Augustine is the first person to study, and his compelling narrative, Confessions, is the best place to start to look into his life.

3. The Shepherd of Hermas

A first-person narrative from some time around the 2nd century, containing visions and parables which are meant to convey deeper Christian theology, The Shepherd of Hermas is cited by early Christian leaders, such as Origen and Irenaeus. Church scholars also believed it was written by several different people and not just the one person, Hermas.

Why you should read it:

The Shepherd of Hermas weaves theology in with personal experience and provides a framework for how many early Christians saw their spirituality. The writer talks about his life as a slave and a shepherd and his journey to Cumae, which brings him closer to continual repentance and to God. It’s sort of like a prelude to Bunyan’s Pilgrim’s Progress. And you know those old cartoons that would show a good angel and a little devil on the character’s shoulders when having to make a moral decision? Well, that idea came from The Shepherd. Beyond that, it was almost considered canon to scripture by a few prominent early Christians because it was a way to convey Christ’s teachings to the common person. Reading it may give you a good allegorical perspective on early Christian theology.

4. The Didache

The Didache which is also called Teachings of the Apostles is one of the oldest surviving documents of canonical teaching we have. It is believed to have been written by a collection of unknown authors some time between the first and second century and contains straightforward guidance on early church practices and ethics. It was pretty much a Christian handbook before the canonization of Scripture.

Why you should read it:

The Didache presents a view of the early church practices that we rarely get to see, and is a very summarized version of the beliefs and rituals that composed the Church. If you want to familiarize yourself with what exact ways the early Christians did church, this a great place to start—right after the book of Acts.

I hope you enjoy these writings and seek to find other ancient Christian writings this year that will edify your own spiritual life.