And it's an Old Testament law.
Bob Lonsberry of WHAM 1180 AM radio asked the Republican front-runner, "Is there a favorite Bible verse or Bible story that has informed your thinking or your character through life?"
"Well, I think many. I mean, you know, when we get into the Bible, I think many. So many," Trump responded.
Then, after internally sorting through the "many, so many" verses that have shaped his character, he chose.
“And some people — look, an eye for an eye, you can almost say that," he said. "That’s not a particularly nice thing. But you know, if you look at what’s happening to our country, I mean, when you see what’s going on with our country, how people are taking advantage of us, and how they scoff at us and laugh at us.”
"And they laugh at our face, and they’re taking our jobs, they’re taking our money, they’re taking the health of our country," he continued. "And we have to be firm and have to be very strong. And we can learn a lot from the Bible, that I can tell you."
The phrase "an eye for an eye" is from Exodus 21:24. If you've read your New Testament, you'll remember Jesus' opinion of this verse was slightly different. In his Sermon on the Mount, Jesus says:
You have heard that it was said, “An eye for an eye and a tooth for a tooth.” But I say to you, Do not resist an evildoer. But if anyone strikes you on the right cheek, turn the other also. — Matthew 5:38-39
Take a listen to the full quote at Buzzfeed.