The image directs to the practice of priests removing all decorations and items from the altar in a Catholic church on Holy Thursday. This is done as a symbolic representation of Jesus Christ's sacrifice and abandonment of his earthly possessions during his crucifixion. The items removed from the altar typically include the altar cloth, candles, crucifix, and other decorative items. This practice is known as "stripping the altar."
Image by sdcason.com - CC-BY-SA 4.0