John 20:23

If you forgive the sins of anyone they are forgiven [because of their faith]; if you retain the sins of anyone, they are retained [and remain unforgiven because of their unbelief].”

Matthew 16:19

I will give you the keys (authority) of the kingdom of heaven; and whatever you bind [forbid, declare to be improper and unlawful] on earth will have [already] been bound in heaven, and whatever you loose [permit, declare lawful] on earth will have [already] been loosed in heaven.”

Matthew 18:18

I assure you and most solemnly say to you, whatever you bind [forbid, declare to be improper and unlawful] on earth shall have [already] been bound in heaven, and whatever you loose [permit, declare lawful] on earth shall have [already] been loosed in heaven.

Mark 2:5-10

When Jesus saw their [active] faith [springing from confidence in Him], He said to the paralyzed man, “Son, your sins are forgiven.”

1 Corinthians 5:4

In the name of our Lord Jesus, when you are assembled, and I am with you in spirit, with the power of our Lord Jesus,

Acts 2:38

And Peter said to them, “Repent [change your old way of thinking, turn from your sinful ways, accept and follow Jesus as the Messiah] and be baptized, each of you, in the name of Jesus Christ because of the forgiveness of your sins; and you will receive the gift of the Holy Spirit.

Acts 10:43

All the prophets testify about Him, that through His name everyone who believes in Him [whoever trusts in and relies on Him, accepting Him as Savior and Messiah] receives forgiveness of sins.”

Acts 13:38-39

So let it be clearly known by you, brothers, that through Him forgiveness of sins is being proclaimed to you;

2 Corinthians 2:6-10

For such a one this punishment by the majority is sufficient,

Ephesians 2:20

having been built on the foundation of the apostles and prophets, with Christ Jesus Himself as the [chief] Cornerstone,

1 Timothy 1:20

Among these are Hymenaeus and Alexander, whom I have handed over to Satan, so that they will be disciplined and taught not to blaspheme.

Treasury of Scripture Knowledge

Summary

Whose soever sins ye remit, they are remitted unto them; and whose soever sins ye retain, they are retained.

Bible References

General references

Matthew 16:19
I will give you the keys (authority) of the kingdom of heaven; and whatever you bind [forbid, declare to be improper and unlawful] on earth will have [already] been bound in heaven, and whatever you loose [permit, declare lawful] on earth will have [already] been loosed in heaven.”
Matthew 18:18
I assure you and most solemnly say to you, whatever you bind [forbid, declare to be improper and unlawful] on earth shall have [already] been bound in heaven, and whatever you loose [permit, declare lawful] on earth shall have [already] been loosed in heaven.
Mark 2:5
When Jesus saw their [active] faith [springing from confidence in Him], He said to the paralyzed man, “Son, your sins are forgiven.”
Acts 2:38
And Peter said to them, “Repent [change your old way of thinking, turn from your sinful ways, accept and follow Jesus as the Messiah] and be baptized, each of you, in the name of Jesus Christ because of the forgiveness of your sins; and you will receive the gift of the Holy Spirit.
Acts 10:43
All the prophets testify about Him, that through His name everyone who believes in Him [whoever trusts in and relies on Him, accepting Him as Savior and Messiah] receives forgiveness of sins.”
Acts 13:38
So let it be clearly known by you, brothers, that through Him forgiveness of sins is being proclaimed to you;
1 Corinthians 5:4
In the name of our Lord Jesus, when you are assembled, and I am with you in spirit, with the power of our Lord Jesus,
2 Corinthians 2:6
For such a one this punishment by the majority is sufficient,
Ephesians 2:20
having been built on the foundation of the apostles and prophets, with Christ Jesus Himself as the [chief] Cornerstone,
1 Timothy 1:20
Among these are Hymenaeus and Alexander, whom I have handed over to Satan, so that they will be disciplined and taught not to blaspheme.