Adam Clarke's Commentary on the Bible

Verse 16 (John 14:16)

I will pray the Father - After having made an atonement for the sin of the world, I will become the Mediator between God and man; and through my mediation and intercession shall all the blessings of grace and glory be acquired.

Another Comforter - The word παρακλητος signifies not only a comforter, but also an advocate, a defender of a cause, a counsellor, patron, mediator. Christ is thus termed, 1 John 2:1 , where the common translation renders the word advocate. Christ is thus called, because he is represented as transacting the concerns of our souls with God; and for this cause, he tells us, he goes unto the Father, John 14:12 . The Holy Spirit is thus called, because he transacts the cause of God and Christ with us, explains to us the nature and importance of the great atonement, shows the necessity of it, counsels us to receive it, instructs us how to lay hold on it, vindicates our claim to it, and makes intercessions in us with unutterable groanings. As Christ acted with his disciples while he sojourned with them, so the Holy Ghost acts with those who believe in his name.

For ever - As the death and atonement of Christ will be necessary to man till the conclusion of the world, so the office of the Holy Spirit must be continued among men till the end of time: therefore says Christ, he shall continue with you for ever, teaching, comforting, advising, defending, and interceding for you and for all my followers to the end of time.

- Adam Clarke's Commentary on the Bible