"One of the puzzles of our humanity is how we are capable of both great cruelty and great kindness," he said, describing what he called the "paradox of human life".
"At one moment, terrible images of human suffering and, in another, heroic acts in war-torn countries where humanitarians of every kind risk their own lives to protect the lives of others."
Referring to a passage from the New Testament, Charles said: "There are three virtues that the world still needs: faith, hope and love. 'And the greatest of these is love."
Charles and Queen Camilla will on Thursday attend the Royal Maundy Service at Durham Cathedral, a ceremony in which 76 men and 76 women receive symbolic gifts of specially minted coins in a centuries-old custom that recognises recipients for their Christian service.
The ceremony is a major fixture on the royal calendar and usually the monarch, who is the head of the Church of England, presents specially minted coins to people recognised for their community service.
The service commemorates Jesus's Last Supper when he washed the feet of his disciples as an act of humility the day before Good Friday.
Charles, who announced his cancer diagnosis the previous February, did not attend the service in Worcester Cathedral in 2024.
with PA
27°C