I don't share my knowledge because I know more, I know more because I share my knowldege
Nothing is an example of the mastery of a knowledge than the ability to teach it. Answering questions increases the knowledge of both person who asked the question and the person providing an answer. Conversely, hoarding knowledge is a sign of little one knows, and hoarding the knowledge is a way to keep something for themselves as a way to show some things others know not of.