Witness

"But you shall receive power when the Holy Spirit has come upon you; and you shall be witnesses to Me in Jerusalem, and in all Judea and Samaria, and to the end of the earth.” Acts 1.8

Nobody needs to receive the Holy Spirit to be healed, delivered from evil or to be prosperous. These miracles are natural wonders of faith in Jesus.
But to an "eyewitness" of His resurrection, a new creature and to possess His character, only by receiving the baptism of the Holy Spirit can you achieve that. He is the One who maintains our salvation until death.

TRANSFIGURED

"And He was transfigured before them. His face shone like the sun, and His clothes became as white as the light."   Matthew 17:2

Surely, the Mount of Transfiguration remained marked in the lives of the three apostles. They saw what they would later experience after receiving the Holy Spirit: transformed life. New spirit, new heart and new character. A character after the Father's, the Son's and the Holy Spirit's own character. This is the transformation that happens when you are born of the Spirit.