Definition:
Repentance is a fundamental concept in Christian theology, referring to the act of turning away from sin and returning to God. To "repent fully" implies a complete and sincere transformation of heart and mind, resulting in a change of behavior and a renewed relationship with God.

Biblical Basis:
The call to repentance is a central theme throughout the Bible. In the Old Testament, the Hebrew word for repentance, "shuv," means to return or turn back, often used in the context of returning to God. In the New Testament, the Greek word "metanoia" signifies a change of mind or purpose, emphasizing a profound transformation.

Old Testament Examples:
The prophets frequently called Israel to repentance. In Joel 2:12-13 , the Lord implores, "Even now," declares the LORD, "return to Me with all your heart, with fasting, weeping, and mourning. Rend your hearts and not your garments. Return to the LORD your God, for He is gracious and compassionate, slow to anger, abounding in loving devotion." This passage highlights the necessity of heartfelt repentance rather than mere external expressions.

New Testament Teachings:
John the Baptist and Jesus Christ both began their ministries with a call to repentance. In Matthew 3:2 , John the Baptist proclaims, "Repent, for the kingdom of heaven is near." Similarly, Jesus echoes this message in Matthew 4:17 , "From that time on Jesus began to preach, 'Repent, for the kingdom of heaven is near.'"

The Apostle Peter, in his sermon at Pentecost, urges the people to repent in Acts 2:38 : "Peter replied, 'Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins. And you will receive the gift of the Holy Spirit.'" This underscores the connection between repentance, forgiveness, and the reception of the Holy Spirit.

Characteristics of Full Repentance:
1. Recognition of Sin: Acknowledging one's sins is the first step toward repentance. Psalm 51:3-4 illustrates this with David's confession: "For I know my transgressions, and my sin is always before me. Against You, You only, have I sinned and done what is evil in Your sight."

2. Godly Sorrow: True repentance involves godly sorrow, which leads to salvation. 2 Corinthians 7:10 states, "Godly sorrow brings repentance that leads to salvation without regret, but worldly sorrow brings death."

3. Confession and Renunciation: Confessing sins and renouncing them is essential. Proverbs 28:13 advises, "He who conceals his sins will not prosper, but whoever confesses and renounces them will find mercy."

4. Transformation and Obedience: Repentance results in a transformed life characterized by obedience to God's commands. Romans 12:2 encourages believers, "Do not be conformed to this world, but be transformed by the renewing of your mind."

5. Restitution and Reconciliation: Where possible, repentance involves making amends and seeking reconciliation. Zacchaeus exemplifies this in Luke 19:8 : "But Zacchaeus stood up and said to the Lord, 'Look, Lord! Here and now I give half of my possessions to the poor, and if I have cheated anybody out of anything, I will pay back four times the amount.'"

The Role of the Holy Spirit:
The Holy Spirit plays a crucial role in the process of repentance, convicting individuals of sin and guiding them toward righteousness. John 16:8 explains, "When He comes, He will convict the world in regard to sin and righteousness and judgment."

Repentance and Salvation:
Repentance is integral to the message of salvation. Acts 3:19 calls for repentance as a means to spiritual renewal: "Repent, then, and turn back, so that your sins may be wiped away, that times of refreshing may come from the presence of the Lord."

Conclusion:
Repentance is not a one-time event but a continual process in the life of a believer. It involves a sincere turning away from sin, a heartfelt return to God, and a commitment to live in accordance with His will. Through repentance, believers experience forgiveness, spiritual renewal, and a deeper relationship with God.