Former president Barack Obama is making his first visit to Africa since leaving the White House to deliver the annual Nelson Mandela Lecture before thousands of South Africans to honor the late anti-apartheid leader on the 100th anniversary of his birth.

Obama has often spoken of how much Mandela influenced him and gave a eulogy at the late president's 2013 memorial service. When Obama was a senator, he had his picture taken with Mandela. When he became president, Mandela kept in his office a copy of the photo that Obama sent him, according to the Associated Press.

From the AP:

The speech on Tuesday, one of Obama’s most high-profile since leaving office, is meant to draw attention to values that today are under threat and to rally people in Africa and elsewhere to push for tolerance and justice. Obama is not expected to make any mention of his successor, President Donald Trump, said Ben Rhodes, Obama’s longtime aide and adviser.

“At the current moment we’re in, values that we thought were well-established — the importance of human rights, respect for diversity — in many parts of the world those values are under threat,” Rhodes told The Associated Press. “Mandela’s life is an inspiring example of how we can overcome obstacles to promote inclusive democracy and an equitable society with tolerance of others.”

Obama, who has spent much of his post-presidency focused on launching his foundation, is also scheduled to participate in a town hall featuring 200 emerging leaders from the Obama Foundation in Africa. Attendees from more than 40 countries will participate in a five-day workshop emphasizing leadership development. Guest speakers include Graca Machel, Mandela's widow; Kofi Annan, the former secretary general of the United Nations; and former Liberian president Ellen Johnson Sirleaf.

Former first lady Michelle Obama left the attendees a video message aimed at encouraging them to aspire to a superior version of Africa.

“Even when the odds are long and the times are dark, change is always possible. But only if we’re willing to work for it and fight for it," she said.

The former president's visit to Africa has not been limited to South Africa. He also made his way to Kenya, the birthplace of his late father, Barack Obama Sr., who worked in politics in the country. Obama spent his trip meeting with Kenyan President Uhuru Kenyatta and was scheduled to attend the opening of a center founded by his half sister, Auma Obama, aimed at providing educational and economic opportunities for young adults to improve their lives.