“Truth is a good dog; but always beware of barking too close to the heels of an error, lest you get your brains kicked out.”
Francis Bacon Sr.
“Battle not with monsters lest you become one.”
Friedrich Nietzsche
“Ye therefore, beloved, seeing ye know these things before, beware lest ye also, being led away with the error of the wicked, fall from your own stedfastness.”
Bible
“Moreover he must have a good report of them which are without; lest he fall into reproach and the snare of the devil.”
“He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you.”
“Mind your speech a little lest you should mar your fortunes.”
William Shakespeare
“Don't be too sweet lest you be eaten up; don't be too bitter lest you be spewed out”
Yiddish Proverb