How does the ring parable in Nathan der Weise compare the three religions?

In Gotthold Ephraim Lessing's play Nathan the Wise, the ring parable serves as a profound argument for religious tolerance. When asked to identify which of the three major religions—Judaism, Christianity, or Islam—is the "true" one, the character Nathan responds with a story about a father who possesses a single, precious ring that grants its wearer the power to be beloved by God and men.1

To avoid showing favoritism among his three sons, the father commissions two identical copies of the ring. Upon his death, each son claims to possess the original, yet none can prove it. The parable suggests that, much like the brothers, followers of the three faiths are engaged in a competition to demonstrate the truth of their religion not through dogma, conflict, or prejudice, but through ethical conduct and humanity.1

Ultimately, the parable implies that the "genuine" ring—and by extension, the true faith—is validated by the virtuous actions of the believer rather than by claims of divine exclusivity.1