1CO 14:22

22 Therefore (strange and ecstatic) languages be into (a) token, not to faithful men, but to men out of the faith; but prophecies be not to men out of the faith, but to faithful men. (And so tongues be a sign, not for men in the faith, but for men out of the faith; and prophecies be a sign, not for men out of the faith, but for men in the faith.)