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?
"Not at all," said Cathy. "We know that Christian values, Biblical values, are important, but we found that it's not an issue of religious labels. We have a wide range of folks that identify with these principles. They have a lot of different religious preferences that are there and it spans the whole gamut. ... They have to be honest, they got to be people of integrity, they got to be passionate about what they're doing -- so we find some of those core values, you know, are common among people of all faiths."
Cathy believes the company's involvement in its employees' lives is good for business, too.
"Well, we genuinely know the full circle of this because if we care enough about them behind the counter, over the long haul, the ambience of that spills over this counter, and customers can kind of sense this: these people are for real.
"I like to tell people the food tastes better on Mondays because we're closed on Sunday. And I generally think that's true -- because a big reason why the food tastes good is because of the warmth and the hospitality that people sense when they are in here."
John Flatley has been with Chick fil-A for 16 years. Now he's the owner-operator of a new restaurant in La Plata, Md.
"The corporate purpose statement meets my personal values, to be a faithful steward of everything God has entrusted to me and to have a positive impact on everyone that comes into contact with Chick fil-A or, in my case, me," said Flatley. "It is just nice to be in a business where that is your focus. It's not about selling chicken, how much money can we make. All those things are important -- if we don't do that, we're not going to be in business. But it's about the opportunity to have a positive influence, whether it's on the team members that I work with, the vendors that we deal with or on the community in general.
"People come up and thank me for being involved in the community, thank me for being closed on Sunday, thank me for the positive impact I've had on their lives, and then they tell us what great food we have.