How do we know that Christ's sacrifice forgives our sins?

The assurance of forgiveness comes from understanding Christ's role as our propitiation. In 1 John 2:2, we learn that Jesus is the propitiation for our sins. This means that through His sacrifice, the wrath of God that was due to us because of our sin was fully satisfied. By believing in Christ and His finished work, we are able to stand before God without guilt or condemnation. His forgiveness is not based on our actions but on His grace and mercy expressed through Christ's death on the cross.