Where did the phrase rest in peace come from?

The phrase "rest in peace" originates from the Latin "requiescat in pace," which was traditionally used in Christian burial rites. It reflects a hope for the deceased to find peace in the afterlife. The phrase has been used in various forms since the early Middle Ages and is commonly inscribed on gravestones and memorials. Its usage has expanded beyond religious contexts to express condolences in secular settings as well.