Throughout his life and ministry, which spanned nearly four decades in the late eighteenth century, the Particular Baptist pastor-theologian Abraham Booth (1734–1806) stressed the necessity of sanctification in the Christian life. In short, he believed that the Holy Spirit’s work of sanctification was an indispensable aspect of the believer’s salvation in Jesus Christ. What were the theological convictions that led him to this conclusion? In exploring this question, this paper will seek to demonstrate that Booth grounded the necessity of sanctification in a Reformed theological framework that emphasized God’s eternal decree to redeem his elect and make them holy. In Booth’s system of thought, sanctification was one of many spiritual blessings that flowed from God’s eternal decree of election, and it was distinct, yet inseparable from other spiritual blessings such as reconciliation, justification, and adoption. In other words, sanctification was one link in an unbreakable “golden chain” of salvation that culminated in the believer’s glorification. In many ways, Booth’s life was a testimony to his belief in the necessity of holiness in the Christina life. Indeed, he was lauded in his own time, and in subsequent generations, as an exemplar of personal piety. However, scholars have given little attention to the question of how Booth formulated his understanding of sanctification within the framework of his Reformed thought. Given Booth’s legacy of personal holiness, and his legacy as a leading theologian of the Particular Baptist movement, his insights on this subject are worthy of consideration. Thus, this paper seeks to offer the first dedicated study of Booth’s understanding of the necessity of sanctification in God’s plan of salvation. In doing so, it hopes to shed further light on the value of his contribution to eighteenth-century Reformed Evangelicalism.