Leviticus 16:30 For on that day shall the priest make an atonement for you, to cleanse you, that ye may be clean from all your sins before the LORD.
The picture was clearly given even in the Old Testament. It was the priest that made the atonement for them. It was the priest who was cleansing them. It was the responsibility of the priest to make sure that they were clean from all their sins.
That is a verse of great joy for us because we know that Jesus came to save us from our sins. He is the One that cleanses us. He is the One that makes atonement for us! Our salvation is His responsibility.Can anything give you more confidence in eternal security than that?