Luke 12:10

"If any one shall speak a word against the Son of man it shall be forgiven him; but he who is blasphemes against the Holy Spirit shall not be forgiven.

Matthew 12:31-32

"Therefore I tell you that every sin and blasphemy shall be forgiven men; but the blasphemy against the Holy Spirit shall not be forgiven.

1 John 5:16

If any one sees his brother committing a sin that is not deadly, he shall ask, and God will give him life, for any one who is not committing a deadly sin. There is a deadly sin; concerning that I do not say that he should pray.

1 Timothy 1:13

although I had formerly been a blasphemer and a persecutor and a doer of outrage. But I obtained mercy because I acted ignorantly in unbelief.

Mark 3:28-30

In solemn truth I tell you that the sons of men shall be forgiven all their sins and all the blasphemies they may utter,

Luke 23:34

Jesus kept saying, "Father forgive them, for they do not know what they are doing." And they divided his garments among them, casting lots for them,

Hebrews 6:4-8

For in the case of those who have been once for all enlightened and have tasted of the heavenly gift,

Hebrews 10:26-31

For if we sin wilfully, after we have received the knowledge of the truth, there no longer remains any other sacrifice for sins,

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
Jesus kept saying, "Father forgive them, for they do not know what they are doing." And they divided his garments among them, casting lots for them,
Matthew 12:31
"Therefore I tell you that every sin and blasphemy shall be forgiven men; but the blasphemy against the Holy Spirit shall not be forgiven.
Mark 3:28
In solemn truth I tell you that the sons of men shall be forgiven all their sins and all the blasphemies they may utter,
1 Timothy 1:13
although I had formerly been a blasphemer and a persecutor and a doer of outrage. But I obtained mercy because I acted ignorantly in unbelief.
Hebrews 6:4
For in the case of those who have been once for all enlightened and have tasted of the heavenly gift,
Hebrews 10:26
For if we sin wilfully, after we have received the knowledge of the truth, there no longer remains any other sacrifice for sins,
1 John 5:16
If any one sees his brother committing a sin that is not deadly, he shall ask, and God will give him life, for any one who is not committing a deadly sin. There is a deadly sin; concerning that I do not say that he should pray.