Luke 12:10

And every one that shall speak a word against the Son of man, it will be forgiven him; but to him that hath blasphemed against the Holy Spirit, it will not be forgiven.

Matthew 12:31-32

Therefore I say to you, All manner of sin and evilspeaking will be forgiven to men; but blasphemy against the Spirit will not be forgiven.

1 John 5:16

If any one see his brother sin a sin not unto death, he shall ask, and shall give him life,to those who sin not unto death. There is a sin unto death; for that I do not say that he shall pray.

1 Timothy 1:13

though formerly I was a blasphemer, and a persecutor, and a doer of outrage; but I obtained mercy, because I did it ignorantly, in unbelief;

Mark 3:28-30

Truly do I say to you, All sins will be forgiven the sons of men, and the blasphemies wherewith they shall blaspheme;

Luke 23:34

And Jesus said, Father, forgive them! for they know not what they do. And they divided his garments, casting lots.

Hebrews 6:4-8

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

Hebrews 10:26-31

For if we sin willingly after we have received the knowledge of the truth, there no longer remaineth 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
And Jesus said, Father, forgive them! for they know not what they do. And they divided his garments, casting lots.
Matthew 12:31
Therefore I say to you, All manner of sin and evilspeaking will be forgiven to men; but blasphemy against the Spirit will not be forgiven.
Mark 3:28
Truly do I say to you, All sins will be forgiven the sons of men, and the blasphemies wherewith they shall blaspheme;
1 Timothy 1:13
though formerly I was a blasphemer, and a persecutor, and a doer of outrage; but I obtained mercy, because I did it ignorantly, in unbelief;
Hebrews 6:4
For it is impossible that those who have once been enlightened, and have tasted of the heavenly gift, and been make partakers of the Holy Spirit,
Hebrews 10:26
For if we sin willingly after we have received the knowledge of the truth, there no longer remaineth a sacrifice for sins;
1 John 5:16
If any one see his brother sin a sin not unto death, he shall ask, and shall give him life,to those who sin not unto death. There is a sin unto death; for that I do not say that he shall pray.