Who said "If you want to master something, teach it."?

This quote is attributed to Richard Feynman.

If you want to master something, teach it. - Richard Feynman

"If you want to master something, teach it."

Richard Feynman Work

Theoretical Physicist American 1918–1988

"The first principle is that you must not fool yourself, and you are the easiest person to fool."

"What I cannot create, I do not understand."

"The pleasure of finding things out is the most important thing."

"You don't have to know everything to do something."

"Hard work never killed anybody."

"Work with purpose and integrity."

"Hard work pays off in the end."

"A man's gotta do what a man's gotta do."