New Life in the Spirit's Power
There are two sides to salvation: Jesus’ death for you and the Spirit’s life in you. Just as Jesus died for you the death you deserved, so the Holy Spirit has come to live in and through you the life you could not attain. As you look to Jesus in love and trust, the Holy Spirit (without any effort on your part) raises you into the new way of life. Walking in the Spirit is a great beginning; supernatural empowerment lies just ahead.
And Peter said to them, "Repent and be baptized every one of you in the name of Jesus Christ for the forgiveness of your sins, and you will receive the gift of the Holy Spirit. Acts 2:38 ESV
Two Tremendous "Promises of the Father"
During the Old Testament period the Holy Spirit was definitely present and powerful, but He was never permanently present within the Israelite believers, nor was His power equally available to them all. A few individuals, for instance, were chosen and anointed by the Spirit of God for specific reasons. Prophets, priest, kings, leaders like the “judge” Samson, craftsmen, and others experienced the Holy Spirit coming “upon” them at certain times or were “anointed” for certain tasks.
God promised that this would change dramatically in the future. The day would surely come when the Lord God would make a way for His Spirit to be placed both “within” and also be poured out “upon” his believing people.
1) The Promise of an Indwelling Presence the Holy Spirit within Us
“I will sprinkle clean water on you, and you shall be clean from all your uncleannesses, and from all your idols I will cleanse you. And I will give you a new heart, and a new spirit I will put within you. And I will remove the heart of stone from your flesh and give you a heart of flesh. And I will put my Spirit within you, and cause you to walk in my statutes and be careful to obey my rules. You shall dwell in the land that I gave to your fathers, and you shall be my people, and I will be your God.” Ezekiel 36:25-28 ESV
In the Upper Room on the evening of the Resurrection as Jesus breathed upon His disciples, they “received” the Holy Spirit. Clearly, at this moment in time they were the first fully “born again” believers in the resurrected Lord. This fulfilled the Father’s promise given through Ezekiel.
And when he had said this, he breathed on them and said to them, "Receive the Holy Spirit. If you forgive the sins of anyone, they are forgiven; if you withhold forgiveness from anyone, it is withheld." John 20:22-23 ESV
2) The Promise of an Empowering Outpour the Holy Spirit upon Us
"And it shall come to pass afterward, that I will pour out my Spirit on all flesh; your sons and your daughters shall prophesy, your old men shall dream dreams, and your young men shall see visions. Even on the male and female servants in those days I will pour out my Spirit.” Joel 2:28-29 ESV
In the Upper Room on the morning of Pentecost (50 days later) many of these same disciples (Thomas was absent) received the outpouring of the Holy Spirit upon them. This fulfilled the Father’s promise given through Joel, which incidentally is the “promise of the Father” Jesus referred to in calling them to pray and wait for "power from on high."
When the day of Pentecost arrived, they were all together in one place. And suddenly there came from heaven a sound like a mighty rushing wind, and it filled the entire house where they were sitting. And divided tongues as of fire appeared to them and rested on each one of them. And they were all filled with the Holy Spirit and began to speak in other tongues as the Spirit gave them utterance. Acts 2:1-4 ESV
Two Ways to Receive the Gift of the Spirit
1) Every Christian receives the gift of the indwelling presence of the Holy Spirit within them through faith-conversion when they repent and turn to Jesus as their Savior. This is the source of our new life in Christ. We are forgiven for our past and we have Jesus living in us through the Holy Spirit. We all receive an equipping for dwelling in Jesus by faith and growing spiritual fruit as we learn to trust and obey Him.
2) Any Christian who desires it can also receive the gift of the outpouring of the Holy Spirit upon them. This baptism of power is the source of our empowerment for the supernatural workings of the Holy Spirit. We can receive an equipping for Jesus to do His deeds of power through us by His Holy Spirit. Being "baptized with power" from on high is available to everyone who believes in the Risen Lord and is willing to seek this further blessing and empowerment.
More to Explore about the Holy Spirit
The Indwelling Presence Surprise! The Holy Spirit of God is now living inside of you! He has always been with you, but now He is in you. This is our “guarantee” that we are indeed going to heaven, but it is so much more. Holy Spirit has been sent to bring into our lives everything necessary for life and right living. It is impossible to live as a true Christian without God’s help and we don’t have to: the Helper is always as close as your next thought.
The Baptism of Power Jesus actually told the first disciples “Don’t leave home without this!” So important is this spiritual empowerment that even the followers who had been trained by Him in person, who had received saving faith and the indwelling Spirit on Easter evening, even these dedicated believers were told to stay in Jerusalem and pray to be “baptized with the Holy Spirit.”  If they needed it, don’t we?
Scriptures and Foot Notes
 The “gold standard” for evidence of having received saving faith is given by Paul in Romans and these disciples would have easily passed on both counts: Because, if you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. For with the heart one believes and is justified, and with the mouth one confesses and is saved. Romans 10:9-10 ESV
 In his on-the-scene explanation of the events of Pentecost Peter specifically identified the promise of the Father in Joel as being the one which Jesus had called them to seek: But Peter, standing with the eleven, lifted up his voice and addressed them, "Men of Judea and all who dwell in Jerusalem, let this be known to you, and give ear to my words. For these men are not drunk, as you suppose, since it is only the third hour of the day. But this is what was uttered through the prophet Joel: ‘And in the last days it shall be, God declares, that I will pour out my Spirit on all flesh, and your sons and your daughters shall prophesy, and your young men shall see visions, and your old men shall dream dreams.’” Acts 2:14-17 ESV
 In this passage from Ephesians Paul writes that believers are sealed with the "promised" Holy Spirit when they believe the gospel. The promise being referred to here is that of Ezekiel 36:25-28--the indwelling Spirit who resides permanently within every believer: In him you also, when you heard the word of truth, the gospel of your salvation, and believed in him, were sealed with the promised Holy Spirit, who is the guarantee of our inheritance until we acquire possession of it, to the praise of his glory. Ephesians 1:13-14 ESV
 We call this secondary experience of Holy Spirit empowerment the "baptism in the Spirit" because Jesus identified this "promise of the Father" as being "baptised with the Holy Spirit": And while staying with them he ordered them not to depart from Jerusalem, but to wait for the promise of the Father, which, he said, "you heard from me; for John baptized with water, but you will be baptized with the Holy Spirit not many days from now." Acts 1:4-5 ESV