In most denominations of Christianity, the Holy Spirit is the third person in the Trinity (along with Father and Son). The Christian Apologetic and Research Ministry defines the Holy Spirit as fully God, omniscient and omnipresent. The Holy Spirit is referred to as a person and not merely a force. The Holy Spirit also has a place in Judaism, Islam and the Bahá'í Faith.
The Old Testament and the Hebrew Bible refer to the Holy Spirit as the "ruach ha-kodesh," or "Spirit of God." It is composed of light and fire, and is known to be fully distinct from God. The New Testament includes 90 specific references to the Holy Spirit. For example, in the Synoptic Gospels, the Holy Spirit appears as early as the birth of John the Baptist. The gospels of Matthew, Mark and Luke all affirm that blasphemy against the Spirit is an unforgivable sin.
In Judaism, the Holy Spirit generally refers to the divine aspect of prophecy and wisdom. The Qur'an makes multiple mentions of the Spirit as an agent of divine action or communication. Some Muslim traditions compare the Spirit with the angel Gabriel. In the Bahá'í Faith, the Holy Spirit is used to describe the transcendence of God's spirit onto prophets and messengers.