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Regarding what has been revealed about the Holy Spirit, Christian beliefs are primarily based on the teachings of Jesus Christ and the writings of the Bible. The New Testament, in particular, contains various passages referring to the Holy Spirit and outlining some of its characteristics and actions.
In the Gospel of John, Jesus promises to send the Holy Spirit as the Advocate or Comforter to guide and teach believers after his departure. The Acts of the Apostles records the coming of the Holy Spirit on the day of Pentecost, when the early Church received the Spirit's empowering presence.
Throughout the New Testament, there are references to the Holy Spirit's role in bestowing spiritual gifts, enabling believers to preach and testify to their faith, and producing fruits of the Spirit, such as love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control.
Moreover, various writings of early Church leaders and theologians have further developed understandings of the Holy Spirit's work and nature. These include the Nicene Creed, which affirms the Holy Spirit's divinity and role in the Trinity.