Here we have, 1. The character given of these seducers and false teachers, They are of the world; that is, men of worldly minds and interests, They speak of the world; that is, they preach a doctrine suitable to the lusts and inclinations of worldly men, who greedily hear them, and easily believe them; ordinarily our words are such as we are; they who are of the world must needs speak of the world, for they have nothing else to speak of. THe covetous man speaks covetously, and the proud man proudly.
Observe, 2. The character which the apostle gives of himself and his fellow-apostles, we are of God; that is, taught and instructed by God. We have our mission and our message from God, and he has given us his attestation, by opening the ears and hearts of those that attend upon our ministry, to receive and embrace our doctrine; but such as are not taught of God, reject both it and us.
Observe, 3. The inference and conclusion which our apostle draws from hence, namely, that by the doctrine and writings of the apostles and evangelists, the truth or falsehood of doctrines may and must be judged; for, says he, Hereby we know the spirit of truth, and the spirit of error; he that knoweth God, heareth us; he that is not of God, heareth not us.