John Calvin on John 8:17-18

17. Even in your law it is written. The argument might, at first sight, appear to be weak, because no man is received as a witness in his own cause. But we ought to remember what I have already said, that the Son of God “Le Fils de Dieu.” ought to be excluded from the ordinary number of other men, “Du nombre commun des autres hommes.” because he neither is a private individual, nor transacts his own private business. As to his distinguishing himself from his Father, by doing so he accommodates himself to the capacity of his hearers, and that on account of his office, because he was at that time a servant of the Father, from whom, therefore, he asserts that all his doctrine has proceeded.