This is as I heard from the Blessed One. At one time the Blessed One was staying in the province of Uruvelā, on the bank of the Nerañjarā River at the root of the Middella tree, after having realized supreme enlightenment. Those days the Blessed One sat cross-legged for seven days experiencing the joy of liberation. One day a great, out-of-season storm-cloud rose up, with seven days of rainy weather, cold winds, and intense darkness. Then the Cobra King Muccalinda left his dwelling place and approached the Blessed One. The Cobra King encircled the Blessed One’s body seven times with its coils. It stood with its great hood spread over the Blessed One’s head, thinking, “Do not let the Blessed One be disturbed by cold. Do not let the Blessed One be disturbed by heat. Do not let the Blessed One be disturbed by the touch of flies, mosquitos, wind, sun, and creeping things.”
At the end of those seven days the Blessed One got out of that concentration. The Cobra King Muccalinda, seeing that the sky had cleared and was free of clouds, unravelled its coils from the body of the Blessed One. It dropped its cobra appearance and took the appearance of a young man. He stood in front of the Blessed One with his hands together, and worshipped the Blessed One.
Then, on realizing the power of loving kindness, the Blessed One spoke the following inspired verses:
“Joyful is the detachment of mind for one who is content, for one who has realized the Dhamma, and who has experienced ultimate freedom, Nibbāna. Joyful is the loving kindness. The harmless mind towards all beings is joyful. Joyful is the Dhamma that leads to dispassion and the overcoming of sense pleasures. The eradication of the conceit “I am” is the supreme joy.”