We may also understand by “the door of the chamber,” the mouth of the body; so that we should not pray to God with loudness of tone, but with silent heart, for three reasons. First, because God is not to be gained by vehement crying, but by a right conscience, seeing He is a hearer of the heart; secondly, because none but thyself and God should be privy to your secret prayers; thirdly, because if you pray aloud, you hinder any other from praying near you.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).