アホにつける薬くすりなし

also: あほうにつけるくすりなし

Meanings

1

there's no cure for stupidity

Proverb meaning that foolishness cannot be fixed. Often used in a resigned or humorous tone. Compare 馬鹿に付ける薬はない.

See also: 馬鹿につける薬はない

何なん度ど注ちゅう意いしても同おなじミスをするなんて、アホにつける薬くすりなしだな。
No matter how many times I warn him, he makes the same mistake. There's no cure for stupidity.