Luke 12:10

And whoever shall speak a word against the Son of Man, it shall be forgiven him. But to him who blasphemes against the Holy Spirit, it shall not be forgiven.

Matthew 12:31-32

Therefore I say to you, All kinds 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 anyone sees his brother sin a sin not to death, he shall ask, and He shall give him life for those that do not sin to death. There is a sin to death, I do not say that he shall pray for it.

1 Timothy 1:13

the one who before was a blasphemer and a persecutor and insolent. But I obtained mercy, because being ignorant, I did it in unbelief.

Mark 3:28-30

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

Luke 23:34

And Jesus said, Father, forgive them, for they do not know what they do. And parting His clothing, they 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
And Jesus said, Father, forgive them, for they do not know what they do. And parting His clothing, they cast lots.
Matthew 12:31
Therefore I say to you, All kinds 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
Truly I say to you, All sins shall be forgiven to the sons of men, and blasphemies with which they shall blaspheme.
1 Timothy 1:13
the one who before was a blasphemer and a persecutor and insolent. But I obtained mercy, because being ignorant, I did it 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 anyone sees his brother sin a sin not to death, he shall ask, and He shall give him life for those that do not sin to death. There is a sin to death, I do not say that he shall pray for it.