For Christ also suffered once for sins, the righteous for the unrighteous, that he might bring us to God, being put to death in the flesh but made alive in the spirit.
1 Peter 3:18
Doctrine affects our behavior. Right doctrine promotes, supports, and strengthens the life of holiness. Wrong doctrinal beliefs deceive, mislead, and burden the Christian life. What we believe about God shapes our choices and actions. We must think rightly and Biblically about God or we may mislead ourselves and others concerning sin, righteousness, and judgement.
Several years back, I worked with a ministry that taught that our past sins were covered by the Cross, but our present and future sins were not. This teaching was intended to promote personal holiness by making our behavior a condition for acceptance with God. However, their teaching caused me to lose my joy: the joy of knowing that my salvation was complete in Christ (Gal. 4:15 NIV).
However, I soon discovered that classic Christian doctrine taught otherwise. All my sin and all your sin is forgiven, put away, and overcome in the Cross. “For by a single offering he has perfected for all time those who are being sanctified” (Heb. 10:14). Every sin committed whether in our past, present, or future is forgiven as we look to Christ in faith. All our present struggles and unknown failures are covered by the blood of Christ. We rejoice for the finished work of Christ on the Cross has met our past, present, and future need for forgiveness (Heb. 10:20-21).
There at Calvary the sin of the world is gathered by the Father, who purposes to save sinners; yes, the sins of the past and the present and the future–because He wants to include you and me who are saved in this great transaction–the sins of the past, present, and future are swept by Almighty power, and as the prophet says, they are caused to meet on the head of His only-begotten Son. The Lord caused to meet upon Him the iniquity of us all. This salvation is rooted in the will of God. We can have boldness to enter into the Holiest through the blood of Jesus, and we can come into the presence of God in the full assurance of faith in the Christ of Calvary.
J. A. Motyer, “One Sacrifice for Sins Forever,†Daily Thoughts from Keswick: A Year’s Daily Readings, ed. Herbert F. Stevenson (London: Hodder and Stoughton, 1980), 358.