Definition:
Active obedience refers to the aspect of Christ's obedience in which He perfectly fulfilled the law of God during His earthly life. This concept is integral to the doctrine of imputed righteousness, where Christ's righteousness is credited to believers, enabling their justification before God.

Biblical Basis:
The doctrine of active obedience is rooted in several key scriptural passages that highlight Christ's fulfillment of the law and His role as the second Adam. In Matthew 5:17, Jesus declares, "Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them, but to fulfill them." This fulfillment is understood as Christ's perfect adherence to the law, which humanity could not achieve due to sin.

Romans 5:19 further elucidates this concept: "For just as through the disobedience of the one man the many were made sinners, so also through the obedience of the one man the many will be made righteous." Here, Paul contrasts the disobedience of Adam with the obedience of Christ, underscoring the salvific impact of Christ's active obedience.

Theological Significance:
Active obedience is a cornerstone of the doctrine of justification by faith. It posits that Christ's perfect obedience to the law is imputed to believers, thus satisfying the righteous requirements of God. This imputation is distinct from Christ's passive obedience, which refers to His suffering and death on the cross. Together, these aspects of obedience form the basis for the believer's justification and reconciliation with God.

Philippians 3:9 emphasizes the importance of this imputed righteousness: "and be found in Him, not having my own righteousness from the law, but that which is through faith in Christ—the righteousness from God on the basis of faith." This passage highlights the believer's reliance on Christ's righteousness rather than their own efforts to fulfill the law.

Historical Context:
The concept of active obedience has been a subject of theological discussion and development throughout church history. It was notably articulated during the Reformation, as reformers like Martin Luther and John Calvin emphasized the sufficiency of Christ's righteousness for salvation. This doctrine was a response to the prevailing views of the time, which often emphasized human merit and works.

Practical Implications:
For believers, the doctrine of active obedience provides assurance of salvation and a foundation for Christian living. It underscores the sufficiency of Christ's work and encourages believers to rest in His completed obedience. This assurance fosters a life of gratitude and service, as believers are motivated by the grace they have received rather than a need to earn God's favor.

In summary, active obedience is a vital component of Christian theology, emphasizing Christ's perfect fulfillment of the law and its implications for the believer's righteousness and relationship with God.