John 16:7

Nevertheless, I tell you the truth;— Though you have not asked the reasons of my going away, I will declare them to you. It is necessary even on your account that I depart; because, if I do not ascend into heaven, and take possession of my mediatorial kingdom, the Comforter, by whose assistance, as I told you before, Ch. John 15:26 you are to convert the world, and who will in a most eminent degree comfort and sanctify your souls, will not be given you: whereas, if I depart, and take possession of my kingdom, I will send him unto you, as the first fruits of the exercise of my kingly power. The word παρακλητος, (see Ch. John 14:16.) signifies not only a Comforter, but an Advocate. Among the Romans, it was usual for those who had any great law-suit, to call their relations and friends to their assistance, who in this office were named advocates. These attended the parties in the court; some assisting them with counsel, others pleading for them, and others barely by their presence giving weight to their cause. Hence the word came not only to signify an advocate, who pleads the cause of another, but a counsellor, a friend, a patron. In this passage the Holy Ghost is called παρακλητος, or advocatus, in the largest sense; because he was to espouse the apostles' cause, to accompany them wherever they went, to defend them from the attacks of their enemies, and to plead for them by their apologies, which he inspired them to deliver in their own behalf; and by the miracles which he enabled them to work in confirmation of their mission; so that he was in the properest sense their friend, counsellor, advocate, patron, and protector. See 1 John 2:1.