The main reason why our Lord must return to the Father was so that the Holy Spirit would come to be with us and within us. John spoke a lot about the Person of the Holy Spirit and His role in the world and in the life of the believer. There are many roles or works of the Person of the Holy Spirit within the Word of God, but I want to point out a few from the Book of John.
For more information on the work and ministry of the Holy Spirit, click on the link and get my book "THE FOUR POSITIONS OF THE HOLY SPIRIT"
Charles Morris. Founder and Senior Pastor of RSIM USA.