The Bible treats blasphemy as a very serious sin, especially when it is directed against God or the Holy Spirit. It covers both words and actions that dishonor or show contempt for God’s name, character, or work.

What blasphemy means

Blasphemy in Scripture is speaking or acting in an irreverent, slanderous, or contemptuous way toward God, God’s name, or God’s works. It can also include falsely accusing God’s servants or attributing God’s work to evil powers.

In a broader biblical sense, blasphemy includes:

• Cursing or mocking God’s name.

• Treating God’s commands with open, willful defiance.

• Slandering Christ or accusing him of evil when he acts with divine authority.

Old Testament teaching

Under the law of Moses, blaspheming the name of the Lord was punishable by death, showing how seriously Israel was to guard God’s holiness. One example is the man who cursed the Name in Leviticus 24 and was stoned by the community.

Blasphemy also appears when Israel worships idols or lives in ways that cause God’s name to be dishonored among the nations, such as with the golden calf episode or prophetic rebukes where God’s name is “slandered” because of Israel’s behavior.

New Testament teaching

In the New Testament, blasphemy still refers to slanderous or irreverent speech about God, Christ, or the things of God. Jesus himself was accused of blasphemy when he forgave sins and claimed divine authority, because his opponents believed he was usurping God’s place.

The apostles also describe blasphemy as a grave sin but highlight that many former blasphemers (such as Paul) received mercy when they turned in faith to Christ. This underscores that ordinary blasphemy, though serious, is not automatically beyond forgiveness when there is repentance and faith.

Blasphemy against the Holy Spirit

Jesus singles out “blasphemy against the Holy Spirit” as uniquely unforgivable, unlike other sins and even other kinds of blasphemy. In context, this refers to attributing the clear, evident work of God’s Spirit in Jesus’ miracles to Satan, in a hardened, knowing rejection of the truth.

This is not a careless word spoken in ignorance, but a settled, willful resistance to the Spirit’s witness about Christ. Scripture links this with a heart that becomes so calloused that it will never repent, which is why there is “no forgiveness” for such a sin.

How the Bible urges believers to respond

Because of the seriousness of blasphemy, the Bible urges:

• Reverence in how people use God’s name and speak about God.

• Care in speech, since “life and death” are described as being in the power of the tongue.

• Confidence in God’s grace, remembering examples like Paul, who had blasphemed yet was forgiven when he believed.

Overall, Scripture presents blasphemy as a grave insult to God’s holiness, warns of the unique danger of hardening against the Holy Spirit, and at the same time holds out mercy for those who turn back in repentance and faith.