Luke 12:10

Every one who shall say anything against the Son of Man will be forgiven, but for him who slanders the Holy Spirit there will be no forgiveness.

Matthew 12:31-32

Therefore, I tell you, men will be forgiven every sin and slander; but slander against the Holy Spirit will not be forgiven.

1 John 5:16

If any one sees his Brother committing some sin that is not a deadly sin, he will ask, and so be the means of giving Life to him--to any whose sin is not deadly. There is such a thing as deadly sin; about that I do not say that a man should pray.

1 Timothy 1:13

though I once used to blaspheme, and to persecute, and to insult. Yet mercy was shown me, because I acted in ignorance, while still an unbeliever;

Mark 3:28-30

I tell you that men will be forgiven everything--their sins, and all the slanders that they utter;

Luke 23:34

[Then Jesus said: "Father, forgive them; they do not know what they are doing."] His clothes they divided among them by casting lots.

Hebrews 6:4-8

For if those who were once for all brought into the Light, and learned to appreciate the gift from Heaven, and came to share in the Holy Spirit,

Hebrews 10:26-31

Remember, if we sin willfully after we have gained a full knowledge of the Truth, there can be no further sacrifice for sin;

Treasury of Scripture Knowledge

Summary

And whosoever shall speak a word against the Son of man, it shall be forgiven him: but unto him that blasphemeth against the Holy Ghost it shall not be forgiven.

Bible References

General references

Luke 23:34
[Then Jesus said: "Father, forgive them; they do not know what they are doing."] His clothes they divided among them by casting lots.
Matthew 12:31
Therefore, I tell you, men will be forgiven every sin and slander; but slander against the Holy Spirit will not be forgiven.
Mark 3:28
I tell you that men will be forgiven everything--their sins, and all the slanders that they utter;
1 Timothy 1:13
though I once used to blaspheme, and to persecute, and to insult. Yet mercy was shown me, because I acted in ignorance, while still an unbeliever;
Hebrews 6:4
For if those who were once for all brought into the Light, and learned to appreciate the gift from Heaven, and came to share in the Holy Spirit,
Hebrews 10:26
Remember, if we sin willfully after we have gained a full knowledge of the Truth, there can be no further sacrifice for sin;
1 John 5:16
If any one sees his Brother committing some sin that is not a deadly sin, he will ask, and so be the means of giving Life to him--to any whose sin is not deadly. There is such a thing as deadly sin; about that I do not say that a man should pray.