I suppose that the phase could be used as another way of saying, “actions speak louder than words.” In this case it could be a much needed corrective to hypocritical preachers. However, I don’t think I’ve ever heard it used this way. In the circles I run in, it is not so much, “practice what you preach,” but, “a well-lived life is a more powerful tool of evangelism than the proclamation of the word.”
As a side note, it is interesting to see the progression of the phrase through the years. I tried to find where exactly St. Francis of Assisi wrote these words, but the best I could find was this short piece:
This quote isn't actually by St. Francis of Assisi. It's certainly Franciscan in spirit but it's adapted from a different quote. "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.” (This information was obtained through "Ask a Franciscan, St. Anthony Messenger.)
Now these words square perfectly well with all we know from the New Testament. I could only wish that these concepts were preached with a superfluity of words often. Not all are called to preach with their tongues, but all are called to proclaim the gospel of Christ with their lives.
However, not being content with changing the words of another to mean something totally different than he ever intended, some have made it even worse by adding the little word “only.” “Preach the Gospel at all times. Only use words if necessary.” This not only goes way beyond what St. Francis of Assisi taught, but it totally perverts the meaning and intention of the Bible.
I hope to post a follow up piece on this shortly. In that post, I'll address the one passage that I can find which supports the quote as most often stated today.