Untilled ground, however rich, will bring forth thistles and thorns; so also the mind of man. - Teresa of Ávila
Josie is a Pye, said Marilla sharply, so she can’t help being disagreeable. I suppose people of that kind serve some useful purpose in society, but I must say I don’t know what it is any more than I know the use of thistles. - L.M. Montgomery
It is good for a man to eat thistles and to remember that he is an ass.
A man that hoards up riches and enjoys them not, is like an ass that carries gold and eats thistles.