"Turnabout is fair play" is a popular phrase that typically means that an action or behavior that was directed towards someone should be reciprocated back towards the original instigator. However, if you are looking for some synonyms to convey the same message, you can consider phrases such as "what goes around comes around," "tit for tat," "an eye for an eye," "you reap what you sow," and "give and take." These idioms all carry a similar sentiment that if a situation is expected to be fair, then each party must show an equal amount of respect and consideration towards the other.