the first turning of the wheel of dharma
Forty-nine days after Buddha attained enlightenment, the gods Brahma and Indra requested him to teach, saying:
O Buddha, Treasure of Compassion,
Living beings are like blind people, in constant danger of falling into the lower realms.
Other than you there is no Protector in this world.
Therefore we beseech you, please rise from meditative equipoise and turn the Wheel of Dharma.
As a result of this request, Buddha rose from meditation and taught the first Wheel of Dharma. These teachings, which include the Sutra of the Four Noble Truths and other discourses, are the principal source of the Hinayana, or Lesser Vehicle, of Buddhism.
Later, Buddha taught the second and third Wheels of Dharma, which include the Perfection of Wisdom Sutras and the Sutra Discriminating the Intention, respectively. These teachings are the source of the Mahayana, or Great Vehicle, of Buddhism.