With accent marks:
Как ау́кнется, так и откли́кнется.
What goes around comes around.
As you treat others, so they will treat you.
This proverb is hard to translate literally. "Аукнется" comes from the sound "ау" that Russian people use to find each other in a forest. "Аукнется" is only used in this proverb, you don't find this word anywhere else. So a close to literal translation can be as follows: as you say "ау", you will receive the same response back.
Other Russian proverbs
Fear has big eyes.
Do not look at a given horse's teeth.
Don’t wave your fists after the fight.
Appetite comes with eating.
One head is good, but two ones are better.
Poor people are inventive.
The apple never falls far from the tree.
The demon is not as scary as he is depicted.