Rabbi Yochanan was suffering from scurvy — a miserable, bleeding affliction of the gums — and the standard remedies were not helping. In desperation he went to a woman skilled in folk medicine and begged for her cure.
She prepared a mixture for him on the fifth and sixth days of the week. But then Rabbi Yochanan raised a worry. "What do I do tomorrow, on Shabbat? I cannot walk all this way to fetch more medicine on the Sabbath."
She assured him one dose would suffice. He pressed her — what if he needed more? She hesitated. "Swear to me you will not reveal the recipe, and I will teach you how to prepare it yourself."
Rabbi Yochanan raised his hand: "By the God of Israel, I will not divulge it." She taught him. The next thing he did was publish the cure — yeast, water, oil, and salt — so that any Jew suffering the same affliction could heal without needing her again.
A Loophole of Holy Cleverness
One Sage in Yoma 84a asks the obvious question — was this not a desecration of God's name, a chillul Hashem? Another Sage defends him with a talmudic sleight of hand: Rabbi Yochanan's oath was that he would not tell the God of Israel. Since he only told humans, he kept his word.
The passage is preserved not as a model of ethics but as a window into how the Sages argued with each other. Medicine, pikuach nefesh (saving life), and the exact weight of an oath all crowd into one anecdote.
Wherever Jewish healing could be shared freely, the Sages preferred it be shared.