Our Lord promises the coming of the Advocate, “the Spirit of truth that proceeds from the Father” (John 15:26). Upon His departure the Advocate, the Spirit, will come. His departure is not an abandonment of His disciples. It rather occasions the coming of the Advocate, the Spirit who will confirm that God’s work is complete. Our Lord says, “For if I do not go, the Advocate will not come to you. But if I go, I will send him to you” (John 16:7).
Our Lord is speaking here of His glorious Ascension and the birth of the Church at Pentecost with the descent of the Holy Spirit. We can easily understand our Lord’s disciples were filled with sorrow (John 16:6), when He told them He was “going to the one who sent [Him]” (John 16:5). But He reassures them that this “departure” should not cause distress or apprehension. They should be confident and hopeful.
When the Advocate comes, “he will convict the world in regard to sin and righteousness and condemnation” (John 16:8). The “world” has rejected our Lord and called Him a sinner (cf. Matthew 9:3). In fact, He is the Redeemer and the Spirit will manifest Him entirely as such. The “world” has denounced our Lord as not being from God (cf. John 9:29). Yet, in returning to His Father, He will prove the “world” wrong (cf. John 16:10). And finally, the “world” is convicted about condemnation, because it condemned our Lord (cf. John 19:6), but it is the Lord who rescues sinners from condemnation. Everything the “world” thought about our Lord is manifestly wrong. The “world” is convicted.
St. Augustine has a beautiful commentary on this verse (John 16:11). He writes, “The devils seeing souls go from hell to heaven, knew that the prince of this world was judged, and being brought to trial in the Savior’s cause, had lost all right to what he held. This was seen on our Savior’s ascension, but was declared plainly and openly in the descent of the Holy Spirit on the disciples” (de Qu. V. et N. Test. Qu. 89).