How do we know that repentance is necessary for Christians?

Repentance is a foundational aspect of the Christian faith, as emphasized in both the Old and New Testaments. In Malachi 3:7, God commands His people to return to Him, which indicates that repentance is required to restore fellowship with God. This call is amplified in the New Testament through the ministry of John the Baptist, who preached repentance for the kingdom of heaven is at hand (Matthew 3:2), and Jesus Himself, who taught that repentance is essential for salvation, as seen in Matthew 4:17. Additionally, the Apostolic message throughout the New Testament consistently affirms the need for believers to repent from sin and turn towards Christ for salvation and sanctification, thereby underlining its continuous importance in the life of a Christian.