14:16 another Comforter. The “Comforter” (Greek parakletos, meaning “called alongside”) is, of course, the Holy Spirit, the third person of the Triune Godhead. Although He is mentioned in many ways in the Old Testament (first of all, as the Energizer of the physical creation, Genesis 1:2), and also in the earlier chapters of the four gospels, this is the first explicit promise that He would be coming to be with the believer, taking the place of the Son, who would be returning to the Father. Having taken a human body, the Son cannot be omnipresent, but the Spirit is omnipresent, and thus Christ can continue to be with each believer through His Holy Spirit.
14:17 Spirit of truth. The “Spirit of Truth” inspired the Holy Scriptures (I Peter 1:11; II Peter 1:21); therefore they are altogether true and righteous (Psalm 19:9).
14:17 in you. The Holy Spirit frequently guided and energized the people of God in ancient times, but, with the death and resurrection of Christ, the way was open for Him to indwell every believer permanently (I Corinthians 6:19; Romans 8:9).