Is God a Trinity? Yes

Who is the Holy Spirit?

If you love me, you will obey what I command. And I will ask the Father, and he will give you another Counselor to be with you forever-- the spirit of truth . . . you know Him for He lives with you and will be in you. John 14:15.

In 1 Samuel 16:13, God Chooses the young David as the next upcoming King, this is David before he kills Goliath. Samuel then anointed him in the presence of his brothers and from that time forward,"the Spirit of the Lord came upon David in power."

The Holy Spirit is God. God consists of the Father, Jesus the Son and the Holy Spirit. The Spirit is the Spirit of God and Jesus. When the Holy Spirit is in us, we have a spiritual life, with God living in us. If He's not in us then He never has been in us or we have quenched Him by grieving Him through our resistance to Him. The Holy Spirit is visibly active throughout the Bible.

In the old Testament

He was very active with the Prophets, supporting them to provide information and direction to the masses. In the New Testament Jesus offers a new covenant in which commandments are written on the hearts of believers enabling them to live better lives. In John 14:26, Jesus says, "the Counselor, the Holy Spirit . . . will teach you all things and remind you of everything. Charles Price notes that the extent to which we repent and not grieve the Spirit dictates the amount of involvement He has in our lives. In Acts 4:13 we note the the priests and Sadducees were amazed at the tremendous courage and confidence Peter and John had. Prior to the death of Jesus they had not been courageous, and Jesus did tell them that after he departed them He would send the Spirit to them.