A Biblical Theology of Cleansing

The book addresses what Harper describes as a central, crucial biblical theme, that many people misunderstand or  skip past, often not considering what it might mean or how it might apply.

After repeatedly encountering the same conversation, Harper saw a gap and the need for more research and writing on this crucial theological theme.

A Whole-Bible Perspective

Harper chose to approach the topic through a biblical theological lens to “take a step back and to see what the whole canon has to say to this question.” This method allows him to address common misconceptions about purity and defilement, both in the Old and New Testament.

“People often assume [defilement] is just an Old Testament thing. It’s just an Israel thing,” Harper explains. “And it kind of mysteriously disappears when you turn from Malachi to Matthew.”

Yet this assumption doesn’t match the biblical evidence. “The New Testament is full of this sort of language about purity and impurity, defilement, cleansing – taking on board that Old Testament heritage,” he notes.

This raises important questions: “What exactly do the New Testament writers mean when they use those terms? Is it the same, is it different? What’s changed?”

The Heart of the Book

At its core, Harper’s book examines purity and impurity as both a human problem and an aspect of God’s saving work.

“Here is both a human problem that we have, but also another mode of God’s salvation – something that he has done on behalf of his people and continues to do on behalf of his people and should rightly lead us to greater praise and worship as we understand God,” Harper says.

“His hope for the book is clear: ‘That overall people will be moved to worship, to maybe see an aspect of God and his work that they haven’t quite seen before.’”

His hope for the book is clear: “That overall people will be moved to worship, to maybe see an aspect of God and his work that they haven’t quite seen before, and turn that into praise and greater understanding of what God has done for his people.”

Practical Implications

The book concludes with three practical applications. Harper explores what atonement means through the lens of defilement and purity. He also addresses the incarnation, beginning with an intriguing question: “Was Jesus ever impure?”

The third application focuses on cross-cultural ministry. Harper notes that “you will do ministry in parts of the world where matters of defilement and cleansing, and purity and impurity, loom large in people’s thinking.”

For Christians serving in such contexts, understanding biblical purity is essential: “If we’re not equipped to talk to people in the language that the Bible uses – things that will meet their very needs and their wonderings and their deepest longings – then we’re not really prepared for gospel work in some parts of the world, including here in parts of Sydney.”

“If we’re not equipped to be able to talk to people in the language that the Bible uses… then we’re not really prepared for gospel work in some parts of the world.”

Harper’s vision is to help Christians “use this part of the Bible, this theme that might be unfamiliar, fueled by books like Leviticus and Numbers, for gospel proclamation, to bring glory to Christ, to help people see why they need him in ways that are resonant with them.”

A Call to Deeper Understanding

You Shall Be Clean invites readers to explore an often neglected dimension of biblical revelation. Through careful theological work, Harper demonstrates how themes of purity and cleansing reveal God’s character and his ongoing work on behalf of his people.

Whether you’re a pastor preparing for cross-cultural ministry, a student of theology, or simply a Christian seeking to understand Scripture more deeply, this book offers fresh insight into a theme that runs throughout the entire Bible.

You Shall Be Clean is available in the New Studies in Biblical Theology series, alongside other SMBC faculty published in the respected series, including Alan Thompson’s The Acts of the Risen Lord Jesus, and Karl Deenick’s Righteous by Promise.

Reviews

“When the psalmist declares that only those who have “clean hands and a pure heart” can ascend into God’s presence (Psalm 24:4), he highlights the significance of the concepts of defilement and cleansing. Addressing this much-neglected topic, Dr Harper skilfully engages with its ubiquitous presence throughout the Bible. By offering new perspectives on the biblical text, this careful study enriches our understanding of the Bible. Importantly, it sheds fresh light on the scope and impact of Christ’s atoning ministry, reminding readers of the necessity of engaging with the whole canon of Scripture.”
— Desmond Alexander, Senior Lecturer in Biblical Studies and Director of Postgraduate Studies, Union Theological College, Belfast

“As one of the leading scholars on Leviticus today, Geoff Harper is well positioned to write a biblical theology of purity and impurity. With tremendous clarity, he shows us what the concepts of purity and impurity mean and how they play out, not just in the Old Testament, but in the entire biblical story. In doing so, he helps us to understand that story better – and does so in a way that is academically strong, theologically rich and pastorally warm. Even in places where I came to different conclusions, Harper still challenged me to see just how pervasive the themes of purity and impurity are – and how important it is to understand them if we are to understand the text. Harper’s book will help you to gain that understanding.”
— Jay Sklar, Professor of Old Testament, Covenant Theological Seminary