In cœlum jacularis.

Threatening those whom you cannot hurt, but whose anger may be highly prejudicial to yourself, is like hurling your dart against the heavens, which it cannot reach, but it may wound you in its return. Chi piscia contra il vento, si bagna la camiscia, and Quien al cielo escupe, en la cara le cae, who casts his spittle against the heavens, will receive it back on his face.