Luke 12:10

And whosoever speaketh a word against the son of man, it shall be forgiven him. But unto him that blasphemeth the holy ghost, it shall not be forgiven.

Matthew 12:31-32

Wherefore I say unto you, All manner of sin and blasphemy shall be forgiven unto men, but the blasphemy of the spirit shall not be forgiven unto men.

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

1 Timothy 1:13

when before I was a blasphemer, and a persecutor, and a tyrant. But I obtained mercy because I did it ignorantly, through unbelief:

Mark 3:28-30

Verily I say unto you, All sins shall be forgiven unto men's children: and blasphemy, wherewith they blaspheme:

Luke 23:34

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

Hebrews 6:4-8

For it is not possible that they which were once lighted, and have tasted of the heavenly gift, and were become partakers of the holy ghost,

Hebrews 10:26-31

For if we sin willingly after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins:

Treasury of Scripture Knowledge

Summary