Hello Throughfaith, the questions that you have presented are really meaningful and well thought especially for understanding salvation. Here is my response to your questions based on scripture.
1. When were our sins paid for? Was it at the cross or the moment we believed?
The book of Hebrews 10:12 says that the Jesus made one sacrifice once and for all for our sins. Therefore our sins were paid at the cross.
However, in terms of Romans 10:9 we receive forgiveness of our sins the moment we believe and not only must we believe, but also confess that Jesus is Lord in order to receive forgiveness.
For example, it is like someone giving you a cheque for 5 million dollars to pay off your debt (so technically you are debt-free and a multi-millionaire), but are only declared debt-free and a multi-millionaire when you accept the cheque and cash it in.
So Jesus paid the price of sin for all mankind at the cross, but it only those who accept Jesus who will receive the declaration that their sins are paid for.
Therefore if an atheist does not believe in Jesus, then his sins will not be forgiven, although Jesus has already paid for his sin.
John 3:18 says “He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God."
2. Were all sins paid for, or only our past sins?
The bible says Jesus has paid for all our sins. Unfortunately it does not tell us what it means by “all”. The bible also does not specify whether it is past and/or future sins that are paid for.
Therefore we need to look at other bible verses in the bible to determine if all or only past sins are forgiven.
Ideally after we have accepted Jesus as our Lord and Savior, we should not continue to sin because we become new creatures (2 Corinthians 5:17). However, we are tempted by the devil (1 Peter 5:8, 1 Thessalonians 3:5) continuously and do commit sin. So are these sins that we commit after we are saved also forgiven?
2.1. .Jesus Christ, our High Priest
In order to answer this question, we have to look at what Jesus is doing right now. The bible says that after Jesus ascended to heaven became our High Priest who is making intercession for us. Now what is the role of a High Priest? His role is to receive the confessed sins of the people and atone for them. Jesus right now receives confessed sins and atones for them and we find grace and mercy because Jesus was also tempted like us and emphasizes with our weaknesses (Hebrew 4:14-16). If all our sins were forgiven (both past and future), then it would not be necessary for Jesus to be our High Priest to atone for our present and future sins.
2.2. Bible asking us to confess our sins
1 John 1:9 says “If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.”
1 John 2:1 says “My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous”
These two bible verses were written to believers and requests them to ask for forgiveness for their sins. If our future sins are already forgiven, then it would not be necessary to make this request. If our future sins are forgiven, then it will also not be necessary for Jesus to be our Advocate and to continuously intercede for our sins.
The bible does not specify whether past and/or future sins, but if you look at 1 John 1:9, and John 2:1 then it is reasonable to conclude that the future sins are not forgiven and therefore our past sins are only forgiven because we are still expected to confess present and future sins. If this was not the case then we will not need Jesus to be our High Priest right now.
Also Jesus taught how we should prayer and gave us the Lord’s Prayer and one of the requests is to ask God to forgive our trespasses (sins) as we forgive those who sin against us. (Luke 11:4, Matthew 6:12). Jesus knew beforehand that he was going to die for sins, but why would he give us the Lord’s pray and state that we must ask God to forgive our sins if both past and future sins will be forgiven after he died on the cross.
Therefore taking the above into consideration it is reasonable to conclude that only past sins are forgiven. And we must ask for forgiveness for our sins that we commit after we are saved.
1. When were our sins paid for? Was it at the cross or the moment we believed?
The book of Hebrews 10:12 says that the Jesus made one sacrifice once and for all for our sins. Therefore our sins were paid at the cross.
However, in terms of Romans 10:9 we receive forgiveness of our sins the moment we believe and not only must we believe, but also confess that Jesus is Lord in order to receive forgiveness.
For example, it is like someone giving you a cheque for 5 million dollars to pay off your debt (so technically you are debt-free and a multi-millionaire), but are only declared debt-free and a multi-millionaire when you accept the cheque and cash it in.
So Jesus paid the price of sin for all mankind at the cross, but it only those who accept Jesus who will receive the declaration that their sins are paid for.
Therefore if an atheist does not believe in Jesus, then his sins will not be forgiven, although Jesus has already paid for his sin.
John 3:18 says “He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God."
2. Were all sins paid for, or only our past sins?
The bible says Jesus has paid for all our sins. Unfortunately it does not tell us what it means by “all”. The bible also does not specify whether it is past and/or future sins that are paid for.
Therefore we need to look at other bible verses in the bible to determine if all or only past sins are forgiven.
Ideally after we have accepted Jesus as our Lord and Savior, we should not continue to sin because we become new creatures (2 Corinthians 5:17). However, we are tempted by the devil (1 Peter 5:8, 1 Thessalonians 3:5) continuously and do commit sin. So are these sins that we commit after we are saved also forgiven?
2.1. .Jesus Christ, our High Priest
In order to answer this question, we have to look at what Jesus is doing right now. The bible says that after Jesus ascended to heaven became our High Priest who is making intercession for us. Now what is the role of a High Priest? His role is to receive the confessed sins of the people and atone for them. Jesus right now receives confessed sins and atones for them and we find grace and mercy because Jesus was also tempted like us and emphasizes with our weaknesses (Hebrew 4:14-16). If all our sins were forgiven (both past and future), then it would not be necessary for Jesus to be our High Priest to atone for our present and future sins.
2.2. Bible asking us to confess our sins
1 John 1:9 says “If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.”
1 John 2:1 says “My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous”
These two bible verses were written to believers and requests them to ask for forgiveness for their sins. If our future sins are already forgiven, then it would not be necessary to make this request. If our future sins are forgiven, then it will also not be necessary for Jesus to be our Advocate and to continuously intercede for our sins.
The bible does not specify whether past and/or future sins, but if you look at 1 John 1:9, and John 2:1 then it is reasonable to conclude that the future sins are not forgiven and therefore our past sins are only forgiven because we are still expected to confess present and future sins. If this was not the case then we will not need Jesus to be our High Priest right now.
Also Jesus taught how we should prayer and gave us the Lord’s Prayer and one of the requests is to ask God to forgive our trespasses (sins) as we forgive those who sin against us. (Luke 11:4, Matthew 6:12). Jesus knew beforehand that he was going to die for sins, but why would he give us the Lord’s pray and state that we must ask God to forgive our sins if both past and future sins will be forgiven after he died on the cross.
Therefore taking the above into consideration it is reasonable to conclude that only past sins are forgiven. And we must ask for forgiveness for our sins that we commit after we are saved.