 Yet they will by no means follow a stranger, but will flee from him, for they do not know the voice of the stranger. Now here's the answer to this question. If you bring all these sheep into the communal sheepfold from all the pastures all around the little city, and it's time to leave with your flock, how do you get your flock back in order? They're not branded. They're not in any way marked. The Bible says the sheep know the voice of the shepherd.