Matthew 6:14-15: Forgiveness:
“For if you forgive other people when they sin against you, your heavenly Father will also forgive you. But if you do not forgive others their sins, your Father will not forgive your sins.”  
This passage establishes a direct connection between our forgiveness of others and God’s forgiveness of us. It emphasizes the importance of extending mercy as a condition for receiving mercy.  

Luke 15:11-32: The Prodigal Son:
This parable is a powerful illustration of God’s unconditional love and forgiveness. The father’s joyful reception of the repentant son symbolizes God’s eagerness to welcome back those who have strayed. It also highlights the importance of repentance and returning to God.

John 20:21-23: The Power to Forgive Sins:
“Jesus said to them again, ‘Peace be with you. As the Father has sent me, I am sending you.’ And with that he breathed on them and said to them, ‘Receive the Holy Spirit. Whose sins you forgive are forgiven them, and whose sins you retain are retained.’”  
This passage underscores the authority given by Jesus to the apostles to forgive sins. It is the foundation for the Sacrament of Penance, where priests act in persona Christi (in the person of Christ) to offer forgiveness.