John 15:26

Christ having spoken of the great opposition which his gospel was likely to meet with in the world, and the hardships that would be put upon the preachers of it, lest any should fear that they and it would be run down by that violent torrent, he here intimates to all those that were well-wishers to his cause and interest what effectual provision was made for supporting it, both by the principal testimony of the Spirit (Joh 15:26), and the subordinate testimony of the apostles (Joh 15:27), and testimonies are the proper supports of truth. I. It is here promised that the blessed Spirit shall maintain the cause of Christ in the world, notwithstanding the opposition it should meet with. Christ, when he was reviled, committed his injured cause to his Father, and did not lose by his silence, for the Comforter came, pleaded it powerfully, and carried it triumphantly. "When the Comforter or Advocate is come, who proceedeth from the Father, and whom I will send to supply the want of my bodily presence, he shall testify of me against those that hate me without cause." We have more in this verse concerning the Holy Ghost than in any one verse besides in the Bible; and, being baptized into his name, we are concerned to acquaint ourselves with him as far as he is revealed. 1. Here is an account of him in his essence, or subsistence rather. He is the Spirit of truth, who proceedeth from the Father.

— Matthew Henry's Concise Commentary (public domain)

(See on Joh 14:15; Joh 14:17).

— Jamieson-Fausset-Brown Commentary (public domain)