Why Jesus must go away

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.

John 16:8 And when he is come, he will reprove the world of sin, and of righteousness, and of judgment: 9 Of sin, because they believe not on me; 10 Of righteousness, because I go to my Father, and ye see me no more; 11 Of judgment, because the prince of this world is judged. 12 I have yet many things to say unto you, but ye cannot bear them now.