Paul’s epistles hold much spiritual wealth and such is Colossians 1:19-20 that says God was pleased to have His fullness dwell in Jesus Christ. Furthermore, because of that, eternal peace through the blood of His cross reconciled all things to Himself.
The problem was sin. It created a barrier between God and man. Before Christ’s finished work you had to follow the law—rules—in order to receive acceptance and approval. But once Jesus took sin upon Himself, the process of reconciliation became real for mankind.
It was God’s doing. Forgiveness of sin was signed and sealed by the blood of Jesus. God reconciled the account of man’s sinfulness against the precious blood of His Son and said it is done, reconciled. It’s like this: you purchase something at a store and agree to pay the amount of the item. The cashier rings it up, and you receive the item. You’re given a receipt that your account has been reconciled—nothing is owed.
No longer is the sin account adding up against you. There’s a zero balance. You’re reconciled with your Heavenly Father in restored fellowship and everlasting love.