The answer is: Thou shalt not commit adultery

Exo 20:14

The seventh commandment, "Thou shalt not commit adultery," has deep roots not just in religious teachings but also in ancient society. Imagine a world without the reliable social contracts we have today—with marriage being one of the few bonds proving fidelity and mutual trust. Committing adultery could disrupt entire families and tribes. This commandment underlines the importance of loyalty not only between spouses but also within the fabric of community life.

Interestingly, this verse, like many in the commandments, is part of broader ancient Near Eastern laws, where fidelity was also emphasized. The Code of Hammurabi, a well-known Babylonian legal text, featured striking parallels that remind us of these shared cultural values across civilizations.

Additionally, in many faith aspects, this command serves as an ethical compass urging individuals to consider the profound consequences of betrayal. It doesn't just pertain to physical acts—it also implicitly addresses loyalty, integrity, and respect in relationships.

In New Testament times, Jesus elevates this commandment in discussions about the heart and intention—digitally challenging society's views by stressing that even lustful thoughts can be seen as a transgression. This hints at a broader moral framework, urging reflections on one's inner life as a path to integrity.

So while we cling to historical meanings, the essence remains: religious loyalty and the workings of love and trust maintain cohesiveness not just in personal deeds, but also in communities relying on such bonds for stability and harmony.