"But ye shall receive power, after that the Holy Ghost is come upon you." (Acts 1:8)
This promise of our Lord signaled the beginning of the immense change from the old covenant to the new. Prior to the fulfillment of Joel’s prophecy (Joel 2:28; Acts 2:16) on the day of Pentecost, the saints of God were empowered both selectively and infrequently.
We, however, upon whom the "better thing" has come (Hebrews 11:40), are all temples of the Holy Spirit (1 Corinthians 6:19). Since we have been "quickened" (made alive) by the Holy Spirit (1 Peter 3:18), we surely should then "walk in the Spirit" (Galatians 5:25). What then is the dunamis (power) that the Holy Spirit provides to us?
Obviously, the power comes from the indwelling presence of the Holy Spirit Himself (Ephesians 3:16-20). Our flesh has "no good thing" (Romans 7:18) to provide for an empowered, Spirit-filled life. Apart from the dwelling of God’s Spirit in us (Ephesians 1:14), we would be unable to live righteously (John 15:5).
But thanks be to the omnipotent and omniscient Creator that the Holy Spirit gives us gifts to use in Christ’s assembly to mature and to encourage each other (Ephesians 4:7-16). The Holy Spirit also grants us the ability to develop His "fruit" in our lives: love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self-control (Galatians 5:22-23).
Then, with the encouragement and maturity we gain through our churches, and the fruit of the Holy Spirit being obvious in our daily lives, the great privilege of sharing the gospel with the lost becomes a delightful exercise of "power" (Romans 1:16) that is clear, not only in careful words of testimony, but in and through a life empowered by the Holy Spirit (1Thessalonians 1:5). HMM III