Deuteronomy 13:3 - Wesley's Explanatory Notes

Thou shalt not hearken to that prophet — Not receive his doctrine, though the sign come to pass. For although when such a sign or wonder foretold did not follow or come to pass, it was a sign of a false prophet, yet when it did come to pass, it was no sufficient sign of a true one, especially, in such a case. There are many things, which may be wrought by evil spirits, God so permitting it for wise and just reasons, not only for the trial of the good, but also for the punishment of ungodly men. Proveth you — That is, trieth your faith and love and obedience. To know — Namely, judicially, or in a publick manner, so as both you and others may know and see it, that so the justice of his judgments upon you may be more evident and glorious.