John 8:18 - Matthew Poole's English Annotations on the Holy Bible

I (saith our Saviour) have two witnesses; I am one, I bear witness of myself; my Father is another, for he beareth witness of me. Our Saviour's argumentation seemeth weak, unless we look upon him as exempt from the condition of ordinary men, and no mere man, by reason of the personal union of the Divine and human nature in his person. Nor must our Saviour be understood here to distinguish himself from his Father, in respect of his Divine being, for so he and his Father are one; but in respect of his office, as he was sent, and his Father was he who sent him. And indeed in the whole he seemeth to accommodate himself to the people's apprehensions of him.