John 8:18

I am one that bear witness of myself - In human courts a man is not allowed to bear witness of himself, because he has a personal interest in the case, and the court could have no proof of the impartiality of the evidence; but in the case of Jesus it was otherwise. When one has no party ends to serve; when he is willing to deny himself; when he makes great sacrifices; and when, by his life, he gives every evidence of sincerity, his own testimony may be admitted in evidence of his motives and designs. This was the case with Jesus and his apostles. And though in a legal or criminal case such testimony would not be admitted, yet, in an argument on moral subjects, about the will and purpose of him who sent him, it would not be right to reject the testimony of one who gave so many proofs that he came from God.

The Father ...beareth witness of me - By the voice from heaven at his baptism Matthew 3:17, and by the miracles which Jesus performed, as well as by the prophecies of the Old Testament. We may here remark:

1. that there is a distinction between the Father and the Son. They are both represented as bearing testimony; yet,

2. They are not divided. They are not different beings. They bear testimony to the same thing, and are one in counsel, in plan, in essence, and in glory.