The Adittapariyaya Sutta, or Fire Sermon, is one of the three cardinal suttas of Theravada buddhism. This sutta concisely lays out some of the most important concepts underlying the Buddha’s 45 years of teaching.
This came just as the Buddha, freshly enlightened, set out on said teaching career to find those with ‘little dust in their eyes’ who could understand the dhamma. He was drawn to a commune of fire-worshiping ascetics who were skilled meditators. However, they believed that their psychic powers were proof of enlightenment.
After unsuccessfully trying to wow them with his superior pyschic powers, the Buddha switched tactics. He gathered them around and sprinkled them with wisdom, reframing the spiritual pursuit from the chasing of teja or heat, to seeking nibbana or coolness. He pointed to the six sense-bases and objects — eye, ear, nose, tongue, body, and mind — and the consciousness, perception, and feeling that arise in conjunction with these senses, and declared: all is burning. Burning with what? With craving. Craving which leads to birth, aging, and death, thereby causing sorrow, lamentation, pain, grief, and despair.
Just upon hearing this sermon, the monks understood and abandoned their craving. And with that there were over a thousand more fully enlightened beings in the world.
https://upavana.org/comic/the-fire-sermon/