Jesus told his disciples that, though he was going to ascend into heaven, he wasn't going to leave them alone. He was going to send "the Advocate", a title for the Holy Spirit. But Jesus wasn't sending the Holy Spirit just to keep us company. Jesus would have the Advocate give us spiritual power so that we might participate in Christ's saving work. Here is the final resurrection reality. The Spirit gives us the ability to raise the spiritually dead to life. We see this happen on Pentecost. The festival of Pentecost was held fifty days after the Passover. (Pentecost is Greek for "fifty".) It was a time to thank God for the harvest. But on that day, through the Church at work, the Holy Spirit gathered another harvest, a harvest of souls. Therefore, Pentecost is the third great festival of the Church, along with the Nativity and the Resurrection. With the Festival of Pentecost, the festival half the Church Year comes to a close.