Since he would no longer be present with them in the flesh, they needed the power of the Holy Spirit to be with them. They receive that empowerment of the Holy Spirit in Acts 2. Peter, the presumably uneducated fisherman, begins to preach from the Prophet Joel and from Psalms. And so the next chapter, the chapter of the church, the believers, our chapter begins.
Believers receive this power from on high, the Holy Spirit, in baptism. Sacramental churches also have Chrismation or Confirmation. Some add the "baptism of the Holy Spirit". Whatever we want to call it, we need the empowering of the Holy Spirit, the third person of the Trinity, to enable us to live the normal Christian life.
For Reflection: Have I been baptized? Am I clothed with power from on high? If not, today is the day. If I have been baptized, do I act like it?
Let us pray. Jesus, I have been baptized in the name of the Father, the Son and Holy Spirit. Help me to live up to it today and every day with the power of the Holy Spirit.