On Monday, Harry and Meghan posted a quote by the anti-apartheid and human rights activist on Instagram, urging their followers to overwhelm the world with "little bits" of good.
It read: "Do your little bit of good where you are; it's those little bits of good put together that overwhelm the world."
Harry and Meghan, who have been vocal on environmental issues, were criticised after reportedly taking four private jet journeys in 11 days.
Sir Elton John has condemned the perceived mistreatment of the royals.
He explained he had provided Harry and Meghan and their son Archie with a private flight to "maintain a high level of much-needed protection".
He wrote on social media that he had made sure the flight was carbon neutral by making the "appropriate contribution" to a carbon footprint fund.
"I am deeply distressed by today's distorted and malicious account in the press surrounding the Duke and Duchess of Sussex's private stay at my home in Nice last week," he said.
"After a hectic year continuing their hard work and dedication to charity, David and I wanted the young family to have a private holiday inside the safety and tranquillity of our home.
"To maintain a high level of much-needed protection, we provided them with a private jet flight.
"To support Prince Harry's commitment to the environment, we ensured their flight was carbon neutral, by making the appropriate contribution to carbon footprint.
He urged the press to stop the "relentless and untrue assassinations on their character that are spuriously crafted on an almost daily basis."
Stay up to date with the latest news stories from a Christian perspective. Sign up to our daily newsletter and receive more stories like this straight to your inbox every morning.
