馬の耳に念仏 (うまのみみにねんぶつ): preaching to the deaf; chanting the nembutsu into a horse's ear

preaching to the deaf; chanting the nembutsu into a horse's ear

For advice wasted on someone who cannot take it in. Blunter than it sounds in English.

The same saying in Chinese: 对牛弹琴

A Japanese proverb (ことわざ)