Luke 12:10

And whoever shall speak a word against the Son of man, it shall be forgiven him: but to him that blasphemeth against the Holy Spirit, it shall not be forgiven.

Matthew 12:31-32

Wherefore I say to you, All manner of sin and blasphemy shall be forgiven to men: but the blasphemy against the Holy Spirit shall not be forgiven to men.

1 John 5:16

If any man shall see his brother sin a sin which is not to death, he shall ask, and he will give him life for them that sin not to death. There is a sin to death: I do not say that he shall pray for it.

1 Timothy 1:13

Who was before a blasphemer, and a persecutor, and injurious: but I obtained mercy, because I did it ignorantly in unbelief:

Mark 3:28-30

Verily I say to you, All sins shall be forgiven to the sons of men, and any blasphemies with which they shall blaspheme:

Luke 23:34

Then said Jesus, Father, forgive them: for they know not what they do. And they parted his raiment, and cast lots.

Hebrews 6:4-8

For it is impossible for those who have been once enlightened, and have tasted the heavenly gift, and have been made partakers of the Holy Spirit.

Hebrews 10:26-31

For if we sin willfully after we have received the knowledge of the truth, there remaineth no more 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
Then said Jesus, Father, forgive them: for they know not what they do. And they parted his raiment, and cast lots.
Matthew 12:31
Wherefore I say to you, All manner of sin and blasphemy shall be forgiven to men: but the blasphemy against the Holy Spirit shall not be forgiven to men.
Mark 3:28
Verily I say to you, All sins shall be forgiven to the sons of men, and any blasphemies with which they shall blaspheme:
1 Timothy 1:13
Who was before a blasphemer, and a persecutor, and injurious: but I obtained mercy, because I did it ignorantly in unbelief:
Hebrews 6:4
For it is impossible for those who have been once enlightened, and have tasted the heavenly gift, and have been made partakers of the Holy Spirit.
Hebrews 10:26
For if we sin willfully after we have received the knowledge of the truth, there remaineth no more sacrifice for sins,
1 John 5:16
If any man shall see his brother sin a sin which is not to death, he shall ask, and he will give him life for them that sin not to death. There is a sin to death: I do not say that he shall pray for it.