Mark 9:40

For he that is not against you, is for you — Our Lord had formerly said, he that is not with me, is against me: thereby admonishing his hearers, that the war between him and Satan admitted of no neutrality, and that those who were indifferent to him now, would finally be treated as enemies. But here in another view, he uses a very different proverb; directing his followers to judge of men's characters in the most candid manner; and charitably to hope that those who did not oppose his cause wished well to it. Upon the whole, we are to be rigorous in judging ourselves, and candid in judging each other.