John 16:5-11 (ESV)
5 But now I am going to him who sent me, and none of you asks me, 'Where are you going?' 6 But because I have said these things to you, sorrow has filled your heart. 7 Nevertheless, I tell you the truth: it is to your advantage that I go away, for if I do not go away, the Helper will not come to you. But if I go, I will send him to you. 8 And when he comes, he will convict the world concerning sin and righteousness and judgment: 9 concerning sin, because they do not believe in me; 10 concerning righteousness, because I go to the Father, and you will see me no longer; 11 concerning judgment, because the ruler of this world is judged.

The disciples were distressed as Jesus foretold what was to happen in the near future. Jesus reassured them this was for the best. While the Jews had the law; the world did not understand sin. After the death of Jesus the Holy Spirit was to come upon the world as a helper to convict those who did not believe in Jesus, to show those who did believe what was right, and to once and for all judge Satan.

A school crossing guard had tried everything to get speeders to slow down. The law was posted, but that did not seem to have any affect. People still continued to speed through the school zone. The crossing guard then took a hair dryer and wrapped it in black electrical tape to mask its identity. As speeders approached the school zone he gave them a gentle reminder by pointing the hair dryer at their car. Instantly they would apply their brakes thinking a radar gun was staring at them. The world knows what sin is, but they often fail to identify their actions with sin. But when the Holy Spirit comes upon them they are shown where they fall short of God�s righteousness. The book of Hebrews says in chapter 101:5-16, �And the Holy Spirit also testifies that this is so. For he says, �This is the new covenant I will make with my people on that day, says the Lord: I will put my laws in their hearts, and I will write them on their minds.�