Luke 12:10

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

Matthew 12:31-32

For this [reason] I tell you, every sin and blasphemy will be forgiven people, but the blasphemy against the Spirit will not be forgiven!

1 John 5:16

If anyone should see his brother sinning a sin not [leading] to death, he should ask, and he will grant life to him, to those who sin not [leading] to death. ([There] is a sin [leading] to death; I do not say that he should ask about that.

1 Timothy 1:13

[although I] was formerly a blasphemer and a persecutor and a violent man, but I was shown mercy because I acted ignorantly in unbelief,

Mark 3:28-30

"Truly I say to you that all the sins and the blasphemies will be forgiven the sons of men, however much they blaspheme.

Luke 23:34

[[But Jesus said, "Father, forgive them, for they do not know what they are doing."]] And they cast lots to divide his clothes.

Hebrews 6:4-8

For [it is] impossible [concerning] those who have once been enlightened, and have tasted the heavenly gift, and become sharers of the Holy Spirit,

Hebrews 10:26-31

For [if] we keep on sinning deliberately 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 said, "Father, forgive them, for they do not know what they are doing."]] And they cast lots to divide his clothes.
Matthew 12:31
For this [reason] I tell you, every sin and blasphemy will be forgiven people, but the blasphemy against the Spirit will not be forgiven!
Mark 3:28
"Truly I say to you that all the sins and the blasphemies will be forgiven the sons of men, however much they blaspheme.
1 Timothy 1:13
[although I] was formerly a blasphemer and a persecutor and a violent man, but I was shown mercy because I acted ignorantly in unbelief,
Hebrews 6:4
For [it is] impossible [concerning] those who have once been enlightened, and have tasted the heavenly gift, and become sharers of the Holy Spirit,
Hebrews 10:26
For [if] we keep on sinning deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins,
1 John 5:16
If anyone should see his brother sinning a sin not [leading] to death, he should ask, and he will grant life to him, to those who sin not [leading] to death. ([There] is a sin [leading] to death; I do not say that he should ask about that.