People who behave wickedly receive their just deserts.

(idiomatic) Alternative form of speak of the devil

People are similar in character to their friends.

(colloquial) A person who uses a rhyming proverb, such as he who smelt it dealt it, in response to a flatus, is likely the one who expelled it.

Alternative form of who pays the piper calls the tune

Alternative form of he who laughs last laughs best

Success is enjoyed more after having previously endured ridicule.

Someone that plans harm or misfortune for others may also inadvertently be the recipient of that same misfortune.

Alternative form of let him who is without sin cast the first stone

When you notice that an enemy is making an error, take care not to interfere with the enemy from completing it so you can take advantage at the right time.