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
Eggs don't teach the chicken.
Start taking care of the dress while it's new, and of your honor while you are young.
The morning is wiser than the evening.
If you are chasing two hares at once, you won’t catch a single one.
The apple never falls far from the tree.
If I knew where I would fall, I would lay some straw there.
Without labor, you can not even catch a fish in the pond.
Fear has big eyes.