What is the origin of the idiom "ride in on a white horse" and when to use it?

The origin of the idiom "ride in on a white horse" can be traced back to medieval legends and folklore, where the image of a knight on a white horse symbolized heroism, chivalry, and rescue. In medieval literature and tales of romance, knights would often ride on white horses to save damsels in distress or to defend the weak and oppressed. It is often used in discussions about unexpected acts of heroism, particularly in challenging or dire situations.