Many people make the mistake of believing that God forgives “little” sins such as lying, anger, and impure thoughts, but does not forgive “big” sins such as murder and adultery. This is not true. There is no sin too big that God cannot forgive it. When Jesus died on the cross, He died to pay the penalty for all of the sins of the entire world (1 John 2:2). When a person places his faith in Jesus Christ for salvation, all of his sins are forgiven. That includes past, present, and future, big or small. Jesus died to pay the penalty for all of our sins, and once they are forgiven, they are all forgiven (Colossians 1:14; Acts 10:43).
We are all guilty of sin (Romans 3:23) and deserve eternal punishment (Romans 6:23). Jesus died for us, to pay our penalty (Romans 5:8). Anyone who believes in Jesus Christ for salvation is forgiven, no matter what sins he has committed (Romans 6:23; John 3:16). Now, a murderer or adulterer will likely still face serious consequences (legal, relational, etc.) for his evil actions – more so than someone who was “just” a liar. But a murderer’s or adulterer’s sins are completely and permanently forgiven the moment he believes and places his faith in Christ.
It is not the size of the sin that is the determining factor here; it is the size of the atoning sacrifice of Christ. If the shed blood of the sinless Lamb of God is sufficient to cover all the sins of all the millions of people who would ever believe in Him, then there can be no limit to the size or types of sins covered. When He said, “It is finished,” sin was made an end of, full atonement and satisfaction for it were given, complete pardon was obtained, peace was made, and redemption from all sin was achieved. It was sure and certain and complete; nothing needs to be, or could be, added to it. Further, it was done entirely without the help of man, and cannot be undone.