The Second Discourse about Dabba

Thus I heard: At one time the Gracious One was dwelling near Sāvatthī, in Jeta’s Wood, at Anāthapiṇḍika’s monastery. There it was that the Gracious One addressed the monks, saying:
“Monks!”
“Reverend Sir!” those monks replied to the Gracious One. And the Gracious One said this:
“While venerable Dabba Mallaputta, monks—after going up into the sky, and sitting in cross-legged posture in the air, in the firmament, entering the fire-element, and emerging—was attaining Complete Emancipation, his body burning and being consumed, there was no charcoal and no ash evident. Just as while ghee or oil is burning and being consumed there is no charcoal and no ash evident, so also while venerable Dabba Mallaputta—after going up into the sky, and sitting in cross-legged posture in the air, in the firmament, entering the fire-element, and emerging—was attaining Complete Emancipation, his body burning and being consumed, there was no charcoal and no ash evident.”
Then the Gracious One, having understood the significance of it, on that occasion uttered this exalted utterance:

“Just as for an iron bar, which is struck by fire and heat,
And gradually cooling, the destiny of that heat is not known,
So it is for those perfectly free, who have crossed over
the flood of bondage to sense pleasures:
There is no known destiny for those who have attained unagitated happiness.”

The Text of the Udāna is Complete