John 16:7
Nevertheless, I tell you the truth; it is expedient for you that I go away; for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you.
These words that Jesus spoke here to His disciples were not the ones that they wanted to hear. They were not excited a bit about His telling them that He was going to go away. Jesus had been there for them for the last three years and had provided everything that they had needed from food to fellowship. He was their Healer and their Helper. The one whom they had learned to depend on and to rely on, their leader and teacher was now saying that He was going to leave them and not only that, but that it was going to be better for them now that He was going away.
Obviously, they did not comprehend what He was talking about, nor did they see any way that it could be better. What they did not pick up on when He was telling them this was that He said that He would ask the Father to send them another Comforter (Helper) and that He would not leave them comfortless (helpless). This Comforter would abide or live with them forever and would be in them. (John 14:16-18)
Now if you will think about this, you will see what a great promise this was. He was saying that while I can only be in one place at a time, He will be with each of you and all believers where ever they are at all times. Then He went on to say that He would not only be with them, He would be in them. Now this is really drastic new revelation to these men. Never before had God dwelt in man. He had been upon, around, over and so forth, but now Jesus was saying that they would never have to be out of the full manifested presence of God as long as they lived. This promise is still true today, Jesus went to be with the Father, but sent us another Comforter who is the Holy Spirit to do in us and for us all that Jesus did for His disciples while He walked upon this earth.