“Preach the Gospel at all times and when necessary use words.”

This quote is of unknown origin. Frequently it is misattributed to St. Francis of Assissi, who nonetheless once stated something fairly similar in sentiment:

Chapter XVII of his Rule of 1221, Francis told the friars not to preach unless they had received the proper permission to do so. Then he added, “Let all the brothers, however, preach by their deeds.” (St Anthony Messenger)