The letter kills

"Who also made us sufficient as ministers of the new covenant, not of the letter but of the Spirit; for the letter kills, but the Spirit gives life." 2 Corinthians 3.6

The abundance of biblical knowledge can give a feeling of well being. If, however, this knowledge is not practiced, it only serves as a witness against you him on the Day of Judgment. The knowledge of the Word sets one free when it is practiced. By practicing it, the Spirit of God works.
Otherwise, what good is to know it? Who in this world knows the Bible better than satan?

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.

Who is who

"But you are not in the flesh but in the Spirit, if indeed the Spirit of God dwells in you. Now if anyone does not have the Spirit of Christ, he is not His." Romans 8.9

In my view, this is one of the most incisive biblical statements. It does not leave room to doubts or discussion. Those who have been possessed by the Spirit of God are so different from those who have not, just as the difference between wine and milk. The behavior of each one bears witness to who is who.

Empowerment

"It is God who arms me with strength, and makes my way perfect."Psalms 18:32

When there's sincerity in seeking the Holy Spirit, it's impossible not to be empowered by God. That's when there are true witnesses of the resurrection of the Lord Jesus Christ.

Witnesses

"And when the Holy Spirit comes on you, you will be able to be my witnesses in Jerusalem, all over Judea and Samaria, even to the ends of the world." Acts 1: 8

When we're filled with the Holy Spirit, we have the right to use the Name of the Lord Jesus to conquer what's impossible, turning us into real witnesses of Him in this Earth.