Blasphemy is generally defined as the act or offense of speaking sacrilegiously about God or sacred things, synonymous with irreverence and disrespect of God or Christ. It is the act of insulting or showing contempt or lack of reverence for God, or claiming the attributes of a deity. Blasphemy is a serious sin that involves speaking with contempt about God or being defiantly irreverent. It is verbal or written reproach of God’s name, character, work, or attributes.

Blasphemy is a term that appears in both the Old and New Testament. According to Smith’s Bible Dictionary, blasphemy in its technical English use signifies the speaking evil of God. In the New Testament, the idea of blasphemy as something that offends the religious sensibilities of others is completely absent. Jesus spoke of a special type of blasphemy—blasphemy against the Holy Spirit—committed by the religious leaders of His day. The situation was that the Pharisees were eyewitnesses to Jesus’ miracles, but they attributed the work of the Holy Spirit to the presence of a demon. Their portrayal of the holy as demonic was a deliberate, insulting rejection of God and was unforgivable.

Blasphemy was punished by stoning in the Old Testament. Fortunately, Jesus forgives even the sin of blasphemy. Blasphemy, by definition, is both deliberate and direct. The unforgivable sin of blasphemy against the Spirit is ongoing hardening of the heart against the Holy Spirit who is trying to lead one to repent of sin and believe in Christ. It is an issue of the heart that manifests in one’s words and actions.