Albert Barnes on John 9:15

The Pharisees asked him how, &c. The proper question to have been asked in the case was whether he had in fact done it, and not in what way. The question, also, about a sinner's conversion is whether in fact it has been done, and not about the mode or manner in which it is effected; yet it is remarkable that no small part of the disputes and inquiries among men are about the mode in which the Spirit renews the heart, and not about the evidence that it is done.