Avatar Book 3(Fire) Episode 13 - The Firebending Masters
After Zuko’s firebending powers weaken substantially, he and Aang go to find the origin of firebending. Although dragons have been extinct since Iroh killed the last one, the first human firebenders may have left behind some hints. Through a series of statues they learn a firebending technique known as the Dragon’s Dance, which triggers a trap. They get caught by Sun Warriors who take them to an altar housing the two original Firebending Masters, the dragons, to be judged. The dragons, finding them worthy of learning their secrets, teach the two the true meaning of firebending, and how the source of the art is not anger, but emotion and drive. After seeing as both Aang and Zuko found worthy, the Sun Warriors reveal that Iroh was also taught the secret of firebending and had lied about killing the two dragons to keep the secret and allow the Sun Warriors to stay hidden from the rest of the world.