PLAINS — “Morning, everybody!” Jimmy Carter called out as he strode into the sanctuary of Maranatha Baptist Church just before 10 a.m. Sunday. “Do we have any visitors this morning?”

The crowd, many of whom had begun lining up outside well before sunrise, erupted in laughter. Most had no way of knowing that this was one of the former president’s favorite opening lines whenever he teaches Sunday school. Fewer still realized they were just this week’s opening act.

Leaving little doubt about his stamina — or his determination, anyway — just three days after receiving radiation treatment for cancer in his brain and after promising his family and the world he was going to ease up on his schedule, Carter, 90, taught back-to-back Sunday school classes. So many people showed up at the little church where the maximum capacity is 460 (including an overflow group watching on a big screen in the assembly hall) that Carter taught one class there, then sped a half-mile down the road to the old Plains High School to do it again for 240 people who had been sent there. Afterwards, he and his wife Rosalynn stood and posed for individual photos with people at the high school, then turned around, returned to the church and spent some 35 minutes doing the same thing with people who’d sat through the first class and Maranatha’s 11 a.m. worship service.

It was no doubt grueling, as he and Mrs. Carter wound up sitting in chairs rather than standing for the second round of photos.

And it was all his idea. Afterwards, though, some friends expressed concern about the strain it put on him.

“He insisted,” said Jan Williams, a Maranatha member and close friend of Carter’s who manages the crowds and logistics of his Sunday school sessions. The two had consulted on Saturday night and decided to hold two classes if necessary.

It was. The first two would-be students showed up on Maranatha’s doorstep at 12:30 a.m. Sunday and never left until the doors opened nearly eight hours later. Well before then, the line had grown so long that police were turning cars around on Hwy. 45 and redirecting them to the high school, now the Jimmy Carter National Historic Site Visitor Center. Even there, not everyone could get in. With the auditorium filled to capacity, some 70 people had to be turned away.

It was at least the second time Carter had taught Sunday school twice in the same day, church members said. But it was the first time he did it against the backdrop of a serious cancer diagnosis. And he didn’t pretend otherwise, opening the session as usual by “telling people where I’ve been.” This time, though, instead of some place in Africa or Latin America he’d visited on behalf of The Carter Center, he told them where he had been was in surgery for a mass on his liver, he said. And then, just last Thursday, having radiation treatment aimed at the four small melanoma spots in his brain.

“But that’s enough about that,” Carter grinned, then launched into a 40-minute class whose main themes concerned loving your enemy and reaching out to God for the strength to bear any sorrow or setback.

“I’m back now, and I intend to keep on teaching at Maranatha as long as I can do it,” he said.

Still, this Sunday may have been unique. Maranatha plans on sending out a statement later this week about how it will handle Carter’s Sunday school lessons going forward, said friend and fellow church member, Jill Stuckey. The church doesn’t like having to turn people away, she said, adding that it’s not “fair” to put students through such an endurance test, especially if it ends up in disappointment for them.

Nor is it fair to their famous teacher, Williams suggested.

“Teaching two classes and taking pictures twice was a strain on him,” she said about Carter. “We’re going to encourage him to listen to his doctors and do what they tell him to do going forward.”