What does the Bible say about blasphemy?

Blasphemy, in biblical terms, generally refers to speaking ill of God or the sacred things of God. In the New Testament, it was a serious accusation against Jesus and His followers, as they were often condemned for declaring Jesus as God. For example, Stephen was accused of blasphemy for preaching the truth of Christ's divinity and for fulfilling Old Testament prophecies related to Jesus. Additionally, the severity of blasphemy was underscored in the teachings of Jesus, who mentioned that blasphemy against the Holy Spirit would not be forgiven.