The arrival of the Holy Spirit at Pentecost was no accident. The Lord planned to unveil Him in a new way at that moment in history because the time was opportune. A large number of people from all over the known world were in the city. Without the right kind of people to witness for Christ, the outpouring of the Holy Spirit could not have occurred. The Holy Spirit responds to the intercessory prayers of God's people for spiritual power.
Intercessory prayer is a special kind of prayer.
It requests specific things from the Lord, based on what He has promised. The Lord does not withhold what He has promised, but He does not always confer it unless we ask for it. Some or all levels may be involved when praying for a specific issue. The Lord honors these prayers, and the Holy Spirit goes into action on our behalf. The experience of the disciples in the upper room before the Day of Pentecost is an example of intercessory prayer in action.