The Spirit of witness
This is the third time Jesus has said to them that the Father will send “the Counsellor” to help them (14:16; 14:26). The Greek word is paracletos, a legal term used for the advocate who comes alongside a defendant in a law court. So the Spirit helps us when we are opposed, giving the words we need (Luke 12:12) and himself bearing witness (another legal word) to the truth about Jesus, both to others and in our own hearts too (26; Rom.8:16).
.
The Spirit doesn’t bear witness alone – he will be the Helper, but the disciples themselves had a responsibility to bear witness to what they knew about Jesus (27). They had been with him “from the beginning” of his ministry so they knew him and his message well, but subsequent believers share equally in the responsibility to witness to their experience of Jesus (17:20).
.
In a court of law, a witness is someone who testifies to what they have seen and heard. They may not be able to speak well but that’s irrelevant! The witness’s role is not to give a speech, preach or argue the case – just to say what they know. So too, as opportunity arises, we are to be witnesses of what Jesus means to us, relying on the Spirit to help us do that fruitfully (1 Pet.3:15).