“ This is a practice As full of labour as a wise man's art: For folly, that he wisely shows, is fit; But wise men, folly-fallen, quite taint their wit. ”
 William Shakespeare, Twelfth Night (1623). copy citation

add

“This fellow's wise enough to play the fool; And, to do that well, craves a kind of wit: He must observe their mood on whom he jests, The quality of persons, and the time; And, like the haggard, check at every feather That comes before his eye. This is a practice As full of labour as a wise man's art: For folly, that he wisely shows, is fit; But wise men, folly-fallen, quite taint their wit. [Enter SIR TOBY BELCH and SIR ANDREW AGUE-CHEEK.]
SIR TOBY. Save you, gentleman.
VIOLA. And you, sir.
SIR ANDREW. Dieu vous garde, monsieur.
VIOLA. Et vous aussi; votre serviteur.
SIR ANDREW. I hope, sir, you are; and I am yours.
” source