The conclusion to Act III of Wagner's music drama Die Walküre has come to be known as the Magic Fire Music. In the final scene, the High God Wotan punishes his Valkyrie daughter, Brünnhilde, by removing her powers as a Goddess and placing her in a deep sleep on a rocky mountain top. She will be doomed to marry any man who wakes her. Brünnhilde is worried she'll be taken by a coward. Feeling some compassion for her, Wotan commands Loge, the fire God, to ignite a ring of magic fire around her and declares that only "one who does not fear my spear" may pass through the fire.
This brief synopsis doesn't begin to cover the complexity of this event in the plot, lol.
Here is, the Magic Fire Music.