Jimmy Carter's legacy lives on through Habitat for Humanity, volunteers say

President Jimmy Carter, who died Sunday at 100, is leaving an enduring legacy in one of the causes he spent decades working on and cherished most, according to those who volunteered with him.

Carter and his wife, Rosalynn Carter, had been "been champions and groundbreaking voices for affordable, decent housing for all" since 1984, according to Habitat for Humanity. The Carters donated their time and influence and worked with nearly 103,000 volunteers in 14 countries to build, renovate and repair 4,331 homes, the nonprofit stated.

Rhode Island-based builder and designer Kenneth Young, 66, first began volunteering with Habitat for Humanity in the 1990s. After his first "Carter build" in 1995 in Watts, California, a neighborhood in southern Los Angeles, he "got the bug," he told ABC News.

Since then, Young has carried out 20 builds, many alongside the 39th president of the United States -- including Carter's last build in Nashville in 2019, Young said.

Young's favorite memory of Carter was during a build in Budapest, Hungary, in 1996, when the residents of a newly built home -- twin boy toddlers -- smacked him in the face with a balloon and Carter, a grandfather himself, "took in it stride" and with a smile.

"It was classic," Young said.

Don Shaw and Thomas Trumble -- lifelong friends who have been volunteering together for decades with the Habitat for Humanity chapter in Hartford, Connecticut, first worked with Carter in 2002 during a build in Durban, South Africa, they told ABC News.

Much of the focus of the build was reconciliation from apartheid, and the project was part of Carter's aim to build 1,000 homes in Africa, Shaw said.

Shaw and Trumble went on to join Carter on builds in Mexico, India, Thailand, Canada and twice in Haiti, they said. They were also with Carter during his last build in Nashville.

The volunteers were often on a first-name basis with Carter, who made them feel like they were part of his "inner-circle," Shaw said.

Although Carter's celebrity and political status often brought a media circus and extra funding, the former president also knew how to get his hands dirty, the volunteers said.

On the job site, Carter was a natural leader, Young said.

Carter's presence alone was enough inspire everyone to work hard and efficiently. The builds run by the Carters were "a logistical miracle," Shaw said, adding that it was often astonishing to see how many homes the group could build within a mere week.

"President Carter, also being a Navy man, and having that military background., he wants it right. He wants it done properly. And he wants it on time," Young said.

Shaw nicknamed Carter the "benevolent taskmaster," he said.

"President Carter was all about getting the job done," Shaw said. "I can remember him going around the site saying, "No photos, no photos. We've got houses to build. Get back."

After an eight-hour work day, the volunteers would come together under a huge camp and share a meal, Trumble said.

One of Carter's favorite rituals was to walk into the completed homes to hand the new occupants the keys and a Bible, Young said.

"He really cares about the people that we're building for," Young said.

Carter will be sorely missed, the volunteers said.

"God knows we're all going to miss President Carter when when he leaves us, but I'm hoping his legacy will continue quite a long way forward," Young said.

Shaw said, "Being around the Carters was just magical."