'Do Not Lie': Man Lives by Biblical Rules for a Year

A.J. Jacobs likes to say he's "officially Jewish," but "in the same way the Olive Garden is an Italian restaurant," he said. And it could be for that reason that the author decided to experience what it means to "live biblically," diving into religion headfirst.

Jacobs lived for one year according to the rules of the Bible. In his book, "The Year of Living Biblically," he writes about interpreting the Bible's rules -- including all the Ten Commandments -- and finding their relevance in the 21st century.

Watch Nightline's Ten Commandments beginning Thursday, Sept. 24 at 11:35 p.m. ET

To explore one 21st century interpretation of the ninth commandment -- "Thou shall not bear false witness against thy neighbor" -- ABC News' David Wright sat down with Jacobs, who said the original meaning of the commandment dealt with perjury.

"If you take it in its original meaning, then it deals with lying on the stand ... perjury. You should not say, 'My neighbor stole a cow,' when he didn't steal the cow," Jacobs explained.

But Jacobs went beyond that, living by the intent of the commandment, which he interpreted to mean: "Do not lie."

"Over the year, it evolved to me that, you should not lie," he said. "So that's what I tried to do, and for a while during my biblical year, I tried to tell no lies whatsoever and it was the worst experience of my life."

Living biblically, Jacobs did away with little white lies like telling his wife she looked great in that dress -- no matter the circumstances or social consequences. He found that complete and utter honesty was dangerous.

"We ran into some friends of my wife's at a restaurant. And they said, 'Ah, we should all get together sometime,' and I felt that I had to tell the truth, so I said, 'You all seem like nice people, but I have absolutely no desire to get together with you. ... I have my own friends I never get to see, so thanks, but no thanks.' And they were offended," Jacobs told ABC News.

"My wife was furious. So furious she wouldn't even look at me," he said. "There are reasons for some lies in life."

Jacobs said that not lying became a "constant confrontation and constant stress" in his life, but helped him realize that he was using lying as a crutch to ease tension or curb friction in a relationship.

"I do think ... it's important to lie sometimes. But, at the same time I learned that I lied too much. ... I am reliant on too many white lies," he told Wright.

"I have cut down on the lies about myself," he said. "So when I make a mistake, I am much more open to say, 'You know what, I screwed up. I am sorry, there's no excuse.' Whereas before I would try to say, 'Oh, you know, my grandfather was in town." Now, I am much more comfortable saying, 'Sorry, I screwed up.'"