The Bible teaches that sin is a state of the heart. It separates us from God. The outward symptoms of sin are the individual sins we commit: lying, cheating, stealing, murder, adultery and so forth.
Islam, on the other hand, teaches that people do not have a fallen nature. There is no original sin. Adam was not rebellious; he just forgot and ate of the forbidden tree. So sin is not spiritual depravity nor is it rebellion against God.
How do Muslims believe they receive forgiveness of sins? By doing good works. For them, redemption is not necessary. Rather, prayer, alms-giving, fasting and so on are the Muslim means of securing forgiveness and gaining God’s favor. ~praying for Muslims/a spiritual warfare calendar
We have been set free because of what Christ has done. Through his blood our sins have been forgiven. We have been set free because God’s grace is so rich. (Ephesians 1:7, NIRV)