The harvest is connected to the pentecost. Phase one of pentecost was the birth of Israel as a nation. Phase two was the birth of the church in the new covenant. Prophetically the feast of pentecost represents the Holy Spirit, infilling, the baptism, and revival. Every time there is a feast there...
Pentecost is the Feast of the Holy Spirit because this is the time when the Holy Spirit came. Pentecost in Hebrew means harvest. The main purpose of the outpouring of the Holy Spirit is to gather the greatest harvest of souls that this world has ever seen.