The atonement and atonement for sins is the payment for sins to do justice and obtain God’s forgiveness. In the Old Testament, propitiation was done by the sacrifice of animals. In the New Testament, Jesus came and became the perfect sacrifice for the sins of the whole world.
God is just and perfect, so he cannot leave sin unpunished. We all sin and the consequence of sin is death and separation from God ( Romans 3:23 ; Romans 6:23 ). Sin must be punished if there is to be justice.
See here: Is God fair?
But God loves us and wants to give us another chance to be with Him. That’s why God gave us another way to pay for our sins: with a substitute. The innocent substitute would die in the transgressor’s place, paying the price for his sins and diverting God’s wrath. Thus, sin would be punished but without destroying the sinner. This is atonement, or atonement.
In the Old Testament the substitute was a flawless animal. The person who repented of his sins sacrificed the animal to God as a propitiation for his sins. But an animal was a poor substitute to atone for a human’s sin. It was necessary to make regular sacrifices because the person continued to sin and the animal could not pay all the sins ( Hebrews 10: 1-4 ). Animal sacrifice was only a symbol of the perfect sacrifice: Jesus.
In the New Testament, God came to earth in the form of a man to pay the price for our sins ( John 1:29 ). God was our replacement. Only God could pay the full price because He alone is perfect, without sin.
See more: why is Jesus called the Lamb of God?
Jesus was the perfect sacrifice. He died for everyone. His death served as a propitiation, because it diverted the punishment for sin from us. Whoever accepts Jesus as his savior has his sins atoned for by his sacrifice; it is clean from sin. It is no longer necessary to offer sacrifices repeatedly, because Jesus paid for all sins ( Hebrews 9: 27-28 ; 1 John 2: 1-2 ). Just repent and ask for forgiveness.