The Buddha's first enlightened lesson - Udana 2.1

Understandably, the first lesson Gotama gave to human students at the Deer Park is cherished, but the very first lesson Gotama gave upon his enlightenment was to Mucalinda, the Snake.

When Gotama just realized full enlightenment at Uruvela, beside the river Neranjara, he sat for a week recovering his strength, experiencing the bliss of freedom. Now, it happened that there came a great rainstorm out of season, with cold winds, and unsettled weather. With this came mosquitoes, gadflies, and all kinds of irritations. So Mucalinda the Snake, King of the Nagas left his palace and encircled Gotama's body with his coils and covered Gotama's head with his cobra hood to keep Gotama warm, sheltered from the rain, wind, mosquitoes, gadflies, and the other unsettled weather and irritants.

When the weather cleared, King Mucalinda removed his coils from Gotama's body and stood before the Buddha, in Bhakti Yoga. Gotama said to the King, "Detachment is blissful - if you are content, have learned the Dharma and see. Such bliss is actually non-affliction; expressed by restraint toward other beings and all irritants. One who overcomes desires for pleasure and aversion to pain is blissful, this is possible by abolishing the conceit of "I am.""