The 1994 Catholic Catechism states that there are varying degrees of sin:
“Sins are rightly evaluated according to their gravity.” Pg. 454, #1854
Catholicism teaches that there are venial sins:
“One commits venial sin when, in a less serious matter, he does not observe the standard prescribed by the moral law, or when he disobeys the moral law in a grave manner, but without full knowledge or without complete consent.” Pg. 456, #1862
Catholicism teaches that there are mortal sins:
“Mortal sin… results in the loss of charity and the privation of sanctifying grace, that is, of the state of grace. If it is not redeemed by repentance and God’s forgiveness, it causes exclusion from Christ’ s kingdom and the eternal death of hell…” Pg. 456, #1861 (See also Pg. 264, #1014, Pg. 269, #1033, Pg. 270, #1035 and Pg. 270, #1037.)
However, with these teachings, the same catechism does not teach the catholic how much repentance it will take to be forgiven of the mortal sin. It does not teach why the Bible does not cover venial and mortal sins. The Bible deals specifically with sin – period.
What does the Bible say sin is?
Whosoever committeth sin transgresseth also the law: for sin is the transgression of the law. 1 John 3:4 Sin is the breaking of the law – the Ten Commandments. All of life’s sins are covered in the Ten Commandments. There is not one among us who can say they have not sinned. We have all broken a command from God! For all have sinned, and come short of the glory of God. Romans 3:23 (emphasis mine). Because we are sinners, we deserve death and hell because we cannot enter Heaven with sin. The wages of sin is death… Romans 6:23 God’s Word does not state here that only a certain type of sin will bring death but plain old sin! This would have been a great opportunity for God to put in His Word the difference between venial and mortal sins. Instead, He chose to state plainly that sin’s payment is death.
In fact, since sin is the transgression of the law, the Word says that if we break even one, we are guilty of them all. For whosoever shall keep the whole law, and yet offend in one point, he is guilty of all. Jas 2:10 (emphasis mine). It does not matter whether you believe there are venial sins or mortal sins, the Word states that you are guilty of all the Law if you have broken just one of them. In other words, if we lie (that is the Ninth Commandment), we have become guilty of breaking all the Commandments (stealing, murder, etc.). God is trying to teach us that any part of the Law that is broken is enough to keep us out of Heaven. That is why Christ had to come – stop and think about this. It is impossible for us to be sinless. We cannot go one day without breaking at least one of the Ten Commandments! But this man (Jesus), after he had offered one sacrifice for sins for ever, sat down on the right hand of God; Hebrews 10:12
It took a sinless sacrifice to pay for our penalty – our wages of death. In whom we have redemption through his blood, even the forgiveness of sins: Colossians 1:14 and For this is my blood of the new testament, which is shed for many for the remission of sins. Matthew 26:28.
Once we confess our sin to God, He is faithful and forgives our sins and remembers them no more! This is a promise! And their sins and iniquities will I remember no more. Hebrews 10:17 There is nothing that we can do (penance) that can help to forgive us and cleanse any further. Once we are forgiven, we are forgiven. There is no differentiating between small and great sins for all sin is an offense to God and we are guilty of all sin even when we break one! Christ died for all sins and there is nothing further that must be done. To say that His shed blood on the cross is not forgiveness enough is to blaspheme the Lord. Is He not perfect? Is He not holy? All that God does is based on His love for us. Even to the point of giving His own sinless blood so that we could be saved. To say that penance will further forgive you or going to purgatory will further purge you is to say that Christ’s shed blood was not enough to pay the penalty. For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; 1 Corinthians 15:3