"Remember the Sabbath day by keeping it holy," the passage reads. "Six days you shall labor and do your work, but the seventh is the Sabbath to the Lord, your God, on it you shall do no work."
But this corporate policy doesn't actually come from biblical teachings. In fact, it has much more practical origins.
One of Cathy's favorite stories -- he tells it often -- is how his father, Truett, opened his first restaurant.
"We opened on a Tuesday, the 23rd of May 1946, but by the time Sunday came, he was exhausted," said Cathy. "He was just worn out. And Sunday was not a big trading day, anyway, at the time. So he was closed that first Sunday and we've been closed ever since.
"He figured if he didn't like working on Sundays, that other people didn't either," Cathy said. "He said, 'I don't want to ask people to do that what I am not willing to do myself.'" Though the closed-on-Sunday rule wasn't really created because of the Biblical fourth commandment, most customers have no trouble believing that it was, thanks to a strong spiritual component in Chick fil-A's corporate philosophy.
Darkness had fallen, but the Dallas grand opening celebration showed no sign of winding down. There was a Happy Birthday shout-out, the usual celebrity responsibilities (signing autographs, getting pictures taken) for Cathy, and free ice cream sundaes.
"We just appreciate what you do corporately and we wanted our sons to meet a really strong Christian businessman that does things right," a woman told Cathy.
Cathy played the trumpet, then climbed on a chair for a serious conversation with the campers gathered inside the restaurant.
"The corporate purpose that Chick fil-A has is something that I would want to put on my tombstone," he said. "That we're here to glorify God by being a faithful steward of all that is entrusted to us and to have a positive influence on all that come into contact with Chick fil-A.
"We had sensed that God's divine direction was in the business and that we wanted to acknowledge that -- the Bible says that, as Solomon says in Proverbs, 'if you acknowledge me in all your ways, I will direct your paths.' And we sensed that God had directed our paths."
Acknowledging that God had directed their paths has been a successful business plan. There are now 1,600 restaurants, with sales growing to about $3 billion this year. It's a tough place to get a job, though.
"It's kind of legendary," Cathy said, laughing, of the interview process required for someone to become an owner-operator of a Chick fil-A. "It's said that it's easier to get a job with the CIA than it is with CFA. And we try to live up to that reputation."
Last year, 25,000 people applied to be owner-operators, the company's version of franchisee. Only 100 were picked, based on Cathy's three C's: competence, chemistry and character.
"Character is very important to us," Cathy said. "People that are values-driven, people that are principles-centered, people who have a sense of who they really are and aren't trying to figure out who they are, but they know who they are."
Is there a fourth C, Christian?