Luke 12:10

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

Matthew 12:31-32

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

1 John 5:16

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

1 Timothy 1:13

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

Mark 3:28-30

Verily I say unto you, All sins shall be forgiven unto the sons of men, and blasphemies whatever they shall blaspheme:

Luke 23:34

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

Hebrews 6:4-8

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