If you are looking for a good study for yourself or a group, I highly recommend Theological Fitness. There are even study questions that can be used in a small group setting. It may not popular these days to be serious about holiness and piety (not to be confused with pietism), but we are in a very real struggle and need to be encouraged in our own fight and to encourage others. This book helps us do that. I am very thankful for Aimee Byrd and her work.

Ah, fitness. Such a hot topic these days. It’s everywhere: from exercise routines to the latest diet trends to electronic gadgets and apps to keep track and stay focused on your goals. Everyone wants to be fit, or at least, laments that they aren’t as fit as they’d like to be. Fitness can be a controversial topic because everyone has a different opinion as to how to go about it.

For example, I hate to run. If you ever see me running, please stop and help me, someone is chasing me. I do, however, enjoy working out in water. This is for three reasons. You don’t get all sweaty. If you make a mistake, no one can see it. And most importantly, if anything jiggles that shouldn’t, they can’t see that either.

Kidding aside, fitness is an important concept in our society. But what about theological fitness? Are our bodies strong, but our “theological muscles” wasting away? Does it matter if they are? What can we do about it? This is the focus of Aimee Byrd’s new book, Theological Fitness: Why We Need a Fighting Faith. Aimee Byrd, also known as the Housewife Theologian, is part of the team of contributors for the Mortification of Spin podcast. She and her co-hosts, Carl Trueman and Todd Pruitt, regularly discuss topics of interest in the Reformed world.

One of Byrd’s recent concerns has been the lack of discernment and doctrinal precision in many of the popular Christian books. I share her concern and am thankful for her solid and helpful contribution in her most recent book.Theological Fitness is an excellent study, and not just for women.

At the heart of Theological Fitness is a discussion of Hebrews 10:23 and what it means for believers. Hebrews 10:23 says, “Let us hold fast the confession of our hope without wavering, for he who promised is faithful.” Byrd writes about how, why, and what we’re to “hold fast” to:

Are you tempted to backslide? Hold fast! Are you being persecuted? Hold fast! Through suffering, fear, and chastisement, and in the ordinary, everyday life of faith and obedience, we are encouraged to hold fast. It may sound like an easy adage, but my goal in this book is to show you that it is a workout. And this kind of workout, this exhortation, in fact, promotes a theological fitness. (14)

What is “theological fitness”? Byrd says, “Theological fitness, then, refers to that persistent fight to exercise our faith by actively engaging in the gospel truth revealed in God’s Word. (16)” Fighting, exercise, actively engaging … these words emphasize the effort we are called to make in our daily walk. It’s about the process of sanctification.

There are some today who prefer not to talk about our efforts as part of sanctification. They point to Christ’s work and our inability. But the idea that we are called to strive towards holiness is not unbiblical. The Westminster Shorter Catechism (Question 35) defines sanctification this way:

Sanctification is the work of God’s free grace, whereby we are renewed in the whole man after the image of God, and are enabled more and more to die unto sin, and live unto righteousness.

Sanctification is God’s work of making us holy, but part of that work is making us able to “die unto sin and live unto righteousness.” And Paul uses frequent examples from sports and warfare to illustrate that this means effort on our part.

Byrd makes this point in Theological Fitness:

We persevere not because of our own faithfulness, but because he who promised is faithful. … Only Jesus had the fitness for the work of our salvation. But he has now qualified us for the race of the Christian life. (17)

I love the image of Jesus having qualified us for the race. It’s God’s work, and He will finish it. But we are called to work, and work hard, in this life. And that is what Byrd focuses on in her book. Using many fitness metaphors and examples, thankfully well-explained for those of us less fitness savvy, Byrd encourages us all to struggle and to fight the good fight.

Because we have been justified by God’s grace and Christ’s death and resurrection, we are now free. Free to struggle against our indwelling sin and free to struggle for growth in holiness:

We are new creations under the reign of grace! Sin no longer reigns in us, and knowing this new status changes everything. We are not fighting to improve our old selves, but we are striving to live as new creations in Christ. (46)

And the struggle is a good thing! It’s a gift:

The great gift of faith doesn’t stop at our justification, but it causes us to continue to trust in God to sanctify us as we press on. That same faith that looked to Christ for a declaration of holiness now looks to him for the strength and ability to live in holiness. Surely, sanctification is not passive process; it is a daily struggle. But the struggle is part of the blessing. (50)

What I loved about this book is that it’s an encouragement, even an exhortation, to be serious about our sanctification, but it’s not a burdensome checklist kind of book. It strikes the right balance between struggling against our sin and resting in the finished work of Christ. Our efforts cannot save us, but we are called to “hold fast” because “He is faithful.”

If you are looking for a good study for yourself or a group, I highly recommend Theological Fitness. There are even study questions that can be used in a small group setting. It may not popular these days to be serious about holiness and piety (not to be confused with pietism), but we are in a very real struggle and need to be encouraged in our own fight and to encourage others. This book helps us do that. I am very thankful for Aimee Byrd and her work.

Rachel Miller is News Editor for the Aquila Report. She is also a homeschooling mother of 3 boys and member of a PCA church. This article first appeared on her blog, A Daughter of the Reformation, and is used with permission.