God promised to pour out His Spirit on His people. When Isaiah spoke of this, noone knew when this would happen. When Jesus arrived on the scene, we began to see some of this promise yet no one, including His disciples, fully understood what the promise meant. Jesus instructed His disciples to wait in Jerusalem until the promise of the Father was manifested. When the Holy Spirit arrived on Pentecost, the disciples knew it and their eyes were opened to all that Jesus had taught them in the previous 3 1/2 years. This same power and Spirit is available to us all today if we but believe and ask.