A Worm proclaimed himself a physician. A Fox asked the Worm how he can cure others when he can’t cure his own appearance.
Note: A similar fable with a Frog instead of a Worm exists.
A Worm put forth his head out of a dunghil, and made proclamation of his skill in physick. Pray, says the Fox, begin with your own infirmities before you meddle with other peoples.
Physician cure thy self.
Saying and doing are two things. Physician cure thy self, preaches to us upon this fable. Every man does best in his own trade, and the Cobler is not to go beyond his last. We have of these dunghil-pretenders, in all professions, and but too many of them that thrive upon their arrogance. If this Worm had met with an Ass to encourage his vanity, instead of a Fox to correct it, he hight have be advand’d to a Doctor of the College perhaps: Or to some more considerable post of honour, either in Church or State.
Gherardo Image from 1480
Vulpes et Vermiculus
Emersus de sterquilinio, vermis coepit profiteri apud animantes se esse medicum summum, neque cedere Paeoni, deorum medico, usu et experientia artis. Quem rugis deformem et nutantem intuita, vulpes “Medice,” inquit, “teipsum curare prius atque ita profiteri artem debueras.”