Good News Translation
When a wicked person curses his enemy he is cursing himself.

New Revised Standard Version
When an ungodly person curses an adversary, he curses himself.

Contemporary English Version
The ungodly fall under any curse that they try to place on their enemies.

New American Bible
When the godless curse their adversary, they really curse themselves.

Douay-Rheims Bible
It is the folly of a man to hearken at the door: and a wise man will be grieved with the disgrace.

It is the folly of a man to hearken at the door: and a wise man will be grieved with the disgrace.

Sirach 21:25
The foot of a fool is soon in his neighbour's house: but a man of experience will be abashed at the person of the mighty.

Sirach 21:26
A fool will peep through the window into the house: but he that is well taught will stand without.

Sirach 21:28
The lips of the unwise will be telling foolish things: but the words of the wise shall be weighed in a balance.

Sirach 21:29
The heart of fools is in their mouth: and the mouth of wise men is in their heart.