Martyn Lloyd-Jones, Romans : Atonement and Justification, 1970, p.19.
How do you know whether a man is a Christian? The answer is that his mouth is “shut”. I like this forthrightness of the Gospel. People need to have their mouths shut, “stopped”. They are forever talking about God, and criticizing God, and pontificating about what God should or should not do, and asking, “Why does God allow this and that?” You do not begin to be a Christian until your mouth is shut, is stopped, and you are speechless and have nothing to say.
Martyn Lloyd-Jones, Romans: Atonement and Justification, 1970, p.19.