His "bark is worse than his bite"
Unfortunately, this is not always true.
To my surprise I learned that the familiar phrase was coined - or collected - by the poet George Herbert. His book of proverbial sayings was published after his death with the memorable title Herbert's Remains.
Herbert was a wonderful poet - unless you are up in arms against God. His mother, who encouraged both her son and John Donne, was also a marvel, as Herbert beautifully acknowledged. You can discover why today is Herbert's feast day here.
In these drear times, with all the wisdom of Adam Smith forgotten, I recommend Herbert's proverbial saying about a mouse.