Charles Spurgeon Commentary John 15:26

"But when the Comforter is come, whom I will send unto you from the Father, [even] the Spirit of truth, which proceedeth from the Father, he shall bear witness of me:" — John 15:26 (ASV)

Whom I'll send unto you from the Father, even the Spirit of truth, which proceedeth from the Father, he shall testify of me:

By this mark you may know whether what has been taught to you is of the Spirit of God. If it does not testify of Christ, if he is not the sum and substance of it all, there is nothing in it for you to accept. If anyone comes to you with what he calls a revelation, if it is not entirely concerning Christ, by this you shall judge it; it is not of the Spirit of God if it does not testify of Christ.