Jesus commanded His followers to stay in Jerusalem to wait the promise (the Holy Spirit) of the Father. Jesus quote what John's saying, Jonh is Baptising water unto repentance and you will baptized with the Holy Spirit. This was fulfilled in the day of Pentecost 120 people gathered together waiting the promised of the Holy Spirit.
Scripture prefference
Acts 1:3-5
Acts 1:8
Acts 2:1-4