Rabbi Yehudah ben Hanina was traveling through Rome when he learned that a Jewish child had been taken captive — a boy of remarkable beauty and already, in his young life, of remarkable learning. The child was held for sale in a Roman slave market.
Yehudah ben Hanina stopped. He gathered what money he could. He ransomed the boy.
That boy, the tradition says, grew up to be Rabbi Ishmael ben Elisha — one of the towering figures of the second-century academy, a priestly sage remembered as one of the Ten Martyrs killed by Rome, and the author of the thirteen hermeneutical principles by which Torah is interpreted in rabbinic literature to this day.
Gaster's Exempla (no. 58, 1924) tells the story in one sentence: "R. Jehuda b. Hanina ransoms from slavery in Rome a child remarkable for his beauty and learning. It is the future R. Ishmael." Everything depends on that ransom. A thousand pages of halakhah hung on whether one anonymous Jew in a market square in Rome would empty his purse for a child he did not know.
The redeeming of captives — pidyon shevuyim — is ranked by Maimonides as the highest form of charity. This story explains why. One ransom can save an entire library that has not yet been written.