Acts 1:8 But you will receive power when the Holy Spirit comes on you; and you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth.”
Acts 4:31 After they prayed, the place where they were meeting was shaken. And they were all filled with the Holy Spirit and spoke the word of God boldly.
The Holy Spirit (the following is from "The Hope of Christmas"
With a sound like a violent wind and amid flames of fire, the long-promised Holy Spirit arrived on the day of Pentecost. The disciples and other Christ-followers witnessed His undeniable presence and continue to do so even today as He gives comfort, wisdom, and power to those who name Jesus as their Lord and Savior.
Once we name Jesus as Lord and receive His Spirit, we then choose daily - if not moment by moment - whether to live in the Spirit, whether to depend on His power, follow His direction and rely on Him to help us die to self. When we make that choice to walk with the Spirit - when we choose to let Him guide us along the narrow path of loving, joyful and freeing friendship with Christ - others will glimpse in us what God is like. And by the Spirit's power, we can resist the temptations of the world, stand strong in God's truth, keep our eyes on the Lord Jesus, and know in our heart of hearts the hope of Christmas.