What is the sacred rule of tarot cards?

Could you please elaborate on the so-called "sacred rule" of tarot cards? Is it a universally accepted principle among tarot practitioners, or does it vary from tradition to tradition? If there is indeed a sacred rule, what are its implications for those who seek guidance from tarot cards? Additionally, how does one ensure that they are adhering to this rule in their tarot practice? I'm eager to gain a deeper understanding of this concept and its significance in the realm of tarot.