A man had publicly dishevelled the hair of a Jewish woman in the street, a humiliating act in the ancient world, where a married woman's covered hair was a point of dignity. Rabbi Akiva sat in judgment and fined the man a substantial sum for the shame he had caused her.
The man sought a way to wriggle out of the fine. Another man advised him: set a trap, make her uncover her own hair in public, and the judge will see that she herself is careless about the matter, so the fine no longer applies.
He followed the advice. He went to her house, stood outside her door, and smashed a jar of olive oil in the street. Oil was precious. She came running out to salvage it, because her family needed it, and in her haste she used her own hair to wipe up the spill. A neighbor was watching. Witnesses could now report that she had exposed her hair voluntarily in the street for a handful of oil.
The man brought the witnesses back to the court and argued, See? She uncovers her own hair in public for a cheap thing. The fine should be canceled.
Rabbi Akiva was not fooled. He gave a ruling that has echoed through Jewish law ever since. Voluntary and forced are different. What a person does of her own free will, in her own house, at her own pace, belongs to her. What is stripped from her by a stranger is a separate injury entirely. The fact that she once chose to uncover her hair for her own purposes does not give another man the right to do it to her in the street.
This short case from Bava Kamma 90a-b, preserved in The Exempla of the Rabbis (Gaster, 1924), is the origin of a principle that still governs rabbinic jurisprudence and modern ethics. Consent is not measured by what a person has done before. It is measured by what they are doing now, in this moment, with full freedom.