Question: where in the bible does it mention the holy ghost?
Answer: New Testament. The term Holy Spirit appears at least 90 times in the New Testament. The sacredness of the Holy Spirit to Christians is affirmed in all three Synoptic Gospels (Matthew 12:30–32, Mark 3:28–30 and Luke 12:8–10) which proclaim that blasphemy against the Holy Spirit is the unforgivable sin.