Holy Lie

A Holy Lie is a philosophical concept coined by Friedrich Nietzsche in his note manuscript "The Will to Power". It is also mentioned in another of Nietzsche's books, "The Antichrist".
Sources.
The idea of a holy lie is seen in part one of the second book of "The Will to Power," which consists of two critiques. The two critiques are "the critique of religion" and "the critique of morality" respectively.
Concept.
A holy lie, according to Friedrich Nietzsche, is the means by which priests and philosophers obtain the piety of their audiences.
Nietzsche argues that the purpose of human action is altered by the holy lie since the original moral standards of the general public is influenced by the moral standards preached by the priests and philosophers. Consequently, the human faculty of moral judgment based on the "beneficial" versus the "harmful" is in dysfunction. People who accept the holy lie do not evaluate the fairness of a thing by what Nietzsche calls "The natural notion". Instead, the notions, standards and doctrines preached by the preachers(priests and philosophers) substitutes the natural notion.
In his book "The Antichrist", Nietzsche further explains his idea with an example of Paul the Apostle and the downfall of the Roman empire.