View source for not to be shaken

δρυὸς πεσούσης πᾶς ἀνὴρ ξυλεύεται → when the oak falls, everyone cuts wood | when an oak has fallen, every man gathers wood | on the fall of an oak, every man gathers wood | when an oak has fallen, every man becomes a woodcutter | one takes advantage of somebody who has lost his strength | one takes advantage of somebody who has lost his power | when the tree is fallen, every man goes to it with his hatchet