Luke 12:10

And everyone who speaks a word against the Son of Man, it will be forgiven him; but he who blasphemes against the Holy Spirit [that is, whoever intentionally discredits the Holy Spirit by attributing the authenticating miracles done by Me to Satan], it will not be forgiven him [for him there is no forgiveness].

Matthew 12:31-32

“Therefore I say to you, every sin and blasphemy [every evil, abusive, injurious speaking, or indignity against sacred things] will be forgiven people, but blasphemy against the [Holy] Spirit will not be forgiven.

1 John 5:16

If anyone sees his brother committing a sin that does not lead to death, he will pray and ask [on the believer’s behalf] and God will for him give life to those whose sin is not leading to death. There is a sin that leads to death; I do not say that one should pray for this [kind of sin].

1 Timothy 1:13

even though I was formerly a blasphemer [of our Lord] and a persecutor [of His church] and a shameful and outrageous and violent aggressor [toward believers]. Yet I was shown mercy because I acted out of ignorance in unbelief.

Mark 3:28-30

“I assure you and most solemnly say to you, all sins will be forgiven the sons of men, and all the abusive and blasphemous things they say;

Luke 23:34

And Jesus was saying, “Father, forgive them; for they do not know what they are doing.” And they cast lots, dividing His clothes among themselves.

Hebrews 6:4-8

For [it is impossible to restore to repentance] those who have once been enlightened [spiritually] and who have tasted and consciously experienced the heavenly gift and have shared in the Holy Spirit,

Hebrews 10:26-31

For if we go on willfully and deliberately sinning after receiving the knowledge of the truth, there no longer remains a sacrifice [to atone] for our sins [that is, no further offering to anticipate],

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 was saying, “Father, forgive them; for they do not know what they are doing.” And they cast lots, dividing His clothes among themselves.
Matthew 12:31
“Therefore I say to you, every sin and blasphemy [every evil, abusive, injurious speaking, or indignity against sacred things] will be forgiven people, but blasphemy against the [Holy] Spirit will not be forgiven.
Mark 3:28
“I assure you and most solemnly say to you, all sins will be forgiven the sons of men, and all the abusive and blasphemous things they say;
1 Timothy 1:13
even though I was formerly a blasphemer [of our Lord] and a persecutor [of His church] and a shameful and outrageous and violent aggressor [toward believers]. Yet I was shown mercy because I acted out of ignorance in unbelief.
Hebrews 6:4
For [it is impossible to restore to repentance] those who have once been enlightened [spiritually] and who have tasted and consciously experienced the heavenly gift and have shared in the Holy Spirit,
Hebrews 10:26
For if we go on willfully and deliberately sinning after receiving the knowledge of the truth, there no longer remains a sacrifice [to atone] for our sins [that is, no further offering to anticipate],
1 John 5:16
If anyone sees his brother committing a sin that does not lead to death, he will pray and ask [on the believer’s behalf] and God will for him give life to those whose sin is not leading to death. There is a sin that leads to death; I do not say that one should pray for this [kind of sin].