What is the origin of the idiom "heart of stone" and when to use it?

The idiom "heart of stone" originates from the idea that a heart, as the symbol of emotion and compassion, should be warm and soft, but when described as "of stone," it signifies a person's lack of empathy, compassion, or emotional responsiveness. It is used to imply that someone is emotionally cold, unfeeling, or indifferent.