The Holy Spirit is the Promise of the Father. Tarry (stay/don’t move) until you receive power from on high. While you sit down, you wait. God did not send you to go and witness but to be the witness.
The Holy Spirit is the power in you to be witnesses to the point of death or dying because of the truth. You can’t be a witness if you’re not ready to die for your faith.
Jesus is the faithful and true witness, the Amen! Jesus is the beginning of Creation, he is God’s beloved Son. The Holy Spirit confirms your testimony.
When you testify of God’s power, mighty miracles will happen. The testimony of Christ must be confirmed in you. Paul was pressed in the Spirit to testify to the Jews that Jesus was Christ. The Spirit of God, moves in you to testify the Gospel of the Grace of God.