"So if you see somebody getting ready to throw a tomato, knock the crap out of them," Trump said at his rally in Cedar Rapids, Iowa.
"I will pay for the legal fees. I promise," he added. "They won’t be so much because the courts agree with us too."
A protestor was arrested last week for throwing tomatoes at Trump at a different Iowa event.
At one point in Monday's rally, Trump asked someone if the crowd, "Do you have a tomato?" It wasn't immediately clear what prompted the question, if the audience member had a tomato or if he or she was removed from the event.