The Book of James, Ch 3 : 1 - 5

"Do not become teachers in large numbers, my brothers, since you know that we who are teachers will incur a stricter judgment. For we all stumble in many ways. If anyone does not stumble in what he says, he is a perfect man, able to rein in the whole body as well. Now if we put the bits into the horses’ mouths so that they will obey us, we direct their whole body as well. Look at the ships too: though they are so large and are driven by strong winds, they are nevertheless directed by a very small rudder wherever the inclination of the pilot determines. So also the tongue is a small part of the body, and yet it boasts of great things."