When did St. Francis say this?
According to appleseeds.org:
This is a great quote, very Franciscan in its spirit, but not literally from St. Francis. The thought is his; this catchy phrasing is not in his writings or in the earliest biographies about him.
In 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."
A few years ago, someone used the Internet to contact some of the most eminent Franciscan scholars in the world, seeking the source of this "Use words if necessary" quote. It is clearly not in any of Francis’ writings. After a couple weeks of searching, no scholar could find this quote in a story written within 200 years of Francis’ death.
On the other hand, I love what he did say: Only preach when you have proper permission, and "Let all the brothers, however, preach by their deeds."
And the sisters.
Good idea. Yeah. Like that.