Luke 12:10

And everyone who speaks a word against the Son of Man, it will be forgiven him; but he who blasphemes against the Holy Spirit, it will not be forgiven him.

Matthew 12:31-32

Therefore I say to you, any sin and blasphemy shall be forgiven people, but blasphemy against the Spirit shall not be forgiven.

1 John 5:16

If anyone sees his brother committing a sin not leading to death, he shall ask and God will for him give life to those who commit sin not leading to death. There is a sin leading to death; I do not say that he should make request for this.

1 Timothy 1:13

even though I was formerly a blasphemer and a persecutor and a violent aggressor. Yet I was shown mercy because I acted ignorantly in unbelief;

Mark 3:28-30

Truly I say to you, all sins shall be forgiven the sons of men, and whatever blasphemies they utter;

Luke 23:34

But Jesus was saying, Father, forgive them; for they do not know what they are doing.” And they cast lots, dividing up His garments among themselves.

Hebrews 6:4-8

For in the case of those who have once been enlightened and have tasted of the heavenly gift and have been made partakers of the Holy Spirit,

Hebrews 10:26-31

For if we go on sinning willfully after receiving the knowledge of the truth, there no longer remains a 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
But Jesus was saying, Father, forgive them; for they do not know what they are doing.” And they cast lots, dividing up His garments among themselves.
Matthew 12:31
Therefore I say to you, any sin and blasphemy shall be forgiven people, but blasphemy against the Spirit shall not be forgiven.
Mark 3:28
Truly I say to you, all sins shall be forgiven the sons of men, and whatever blasphemies they utter;
1 Timothy 1:13
even though I was formerly a blasphemer and a persecutor and a violent aggressor. Yet I was shown mercy because I acted ignorantly in unbelief;
Hebrews 6:4
For in the case of those who have once been enlightened and have tasted of the heavenly gift and have been made partakers of the Holy Spirit,
Hebrews 10:26
For if we go on sinning willfully after receiving the knowledge of the truth, there no longer remains a sacrifice for sins,
1 John 5:16
If anyone sees his brother committing a sin not leading to death, he shall ask and God will for him give life to those who commit sin not leading to death. There is a sin leading to death; I do not say that he should make request for this.