give someone a taste of their own medicine

Origin

The idiom "a taste of your own medicine" emerged from a time when medicine was often a bitter, unpalatable concoction, and the belief was that the doctor's remedy, no matter how foul, was the path to a cure. But what if the doctor themselves needed a cure? The phrase, first recorded in the 17th century, quickly became a popular way to describe the satisfying moment when a person experienced the very same unpleasantness or ill-treatment they had inflicted on others. It wasn't just about fairness; it was a potent image of poetic justice, suggesting that those who dispensed harsh "medicine" to others would eventually have to swallow their own bitter dose. The concept resonated universally: if you dish it out, you should be able to take it.