Towards the end of the Last Supper Discourse, Jesus begins to tell his disciples of persecutions yet to come (John 15:28ff). He speaks of these so that the disciples may not be scandalized (John 16:1). During their period of tribulation, the disciples will be sad while all around them all will rejoice (John 16:20). But this will be temporary, like the suffering of a woman giving birth. After a while, they will rejoice with a joy no one can take from them (Jn. 16:23). And though the hour comes near when someone will strike the shepherd and they, the sheep, will be scattered, still they shouldn't be afraid. Because Jesus, the Lord, has overcome the world (Jn. 16:33).
Within the context of these encouraging words, Jesus speaks of the other Advocate who will come in His name. In 14:26, he had said that the Holy Spirit will remind the disciples of these words about future events when these do occur. At the same time, the Spirit of Truth will be giving witness to Jesus in those difficult times as He accompanies the disciples when they too give witness to the Lord (Jn. 16:27). Jesus will send the Paraclete who will vindicate Him, His work and condemn the prince of this world (16:7-11). Finally, while Jesus is away, the Spirit of Truth will continue to teach the disciples as Jesus did. In this regard, John's use of two verbs is to be noted lalew laleo ("I speak") and anaggellw anaggello ("I report/proclaim")
The verb laleo is the same verb that is used in John 14-17 to designate Jesus speaking (Jn. 14:25.30; 15:3.11; 16:1.4.6.18.25.29.33; 17:1.13). On the other hand, anaggello is used in Jn. 4:25 as the action of the Messiah who reveals all. In other words, the Paraclete not only extends the presence of Jesus among the disciples. He also continues the function of the Messiah as "revealer". This function is further elaborated in the verb odegew odegeo ("I lead/guide") with the object "to all truth". The Paraclete will be the guide to the revelations of Jesus who had introduced Himself before as "the Truth" (14:6)
Jesus had earlier said that the Paraclete will remind the disciples of the things he has announced (14:26). This time, he says that the Paraclete will reveal "coming things". The phrase anaggelei umin with Spirit of Truth as subject appears three times: first with the object "things to come", second, with the object "from what is mine" and third as a direct quote after the clarification "All that the Father has is mine.". In sum, the Paraclete is the one who elaborates on those things that the Father reveals through the Son. The Son is the final revelation of the Father but the Spirit deepens the understanding of the disciples of that revelation.
John 16:12-15 is the gospel selection for the Solemnity of the Holy Trinity which, at the end of the Easter season, celebrates the work of the Father, Son and Holy Spirit in salvation history. The selction is accompanied by Romans 5:1-5 in which Paul describes how the Christian, redeemed by the Son, possesses the love of God in his heart through the Holy Spirit and is able to stand at peace before God himself, inspite of the tribulations he may be encountering.1
The choice of John 16:12-15 underscores the role of the Holy Spirit in helping the Church reach its understanding of the Triune God. The doctrine of the Trinity, hinted at in the Scriptures and finally expressed in the sentence "Three Persons, One God" is the work of the Spirit leading the Church "to all Truth".
The mission of the Holy Spirit, sent by the Father in the name of the Son (Jn. 14:26) and by the Son "from the Father" (Jn. 15:26), reveals that, with them, the Spirit is the one and the same God. "With the Father and the Son he is worshipped and glorified" (Nicene Creed) CCC, par. 263
1The OT reading comes from Prov. 8:22-31 and emphasizes how God's wisdom precedes all of Creation which was made through it. It is included in the liturgy because it was the same text used by the Arians in showing how the Son (God's Wisdom) was created. It is to be noted however that in the poetry of Proverbs, what is underlined is the precedence in time of Wisdom.
