A short, chilling ma'aseh from the rabbinic tradition, preserved as exemplum no. 73 in Moses Gaster's 1924 collection The Exempla of the Rabbis, makes its point in a handful of sentences.
A man and a woman, betrothed to each other under Jewish law but not yet fully married, were taken captive in a raid and sold into slavery. Their master, either unaware of their relationship or indifferent to it, housed them together in the same quarters. They lived as slaves side by side for a long time. And yet, through every night of their captivity, they refused to become intimate. The betrothal bond — even under conditions of total coercion — held. Neither would touch the other until they could be properly married.
The Rabbis contrast this couple with a horrifying case from the same era: a father and his son who together sinned with a betrothed woman on Yom Kippur. Three transgressions at once — the sanctity of a betrothed, the bond between father and son, and the holiness of the Day of Atonement. The Rabbis teach that the trio was found out and punished with death.
The juxtaposition is the whole teaching. In the first case, two slaves with no rights, no property, no privacy, and no legal protection maintained the purity of a betrothal through sheer will. In the second, free men at the peak of social power violated every law available to them on the holiest day of the year. The Rabbis were not naive about human behavior. They knew that circumstance does not make a person righteous or wicked. What makes a person righteous, these paired stories insist, is what the person chooses when no one is watching and every structure that used to enforce the choice has collapsed. The captives kept their vow because the vow was theirs, not because anyone could make them keep it.