Appāyukasuttaṃ [Ud 5.2, PTS 48]

2.

The Discourse on the Short-Lived

42. Thus have I heard - On one occasion the Blessed One was dwelling at Sāvatthī in Jeta's Grove, Anāthapiṇḍika's park. Then the Venerable Ānanda, in the afternoon, having emerged from seclusion, approached the Blessed One; having approached, he paid respect to the Blessed One and sat down to one side. Seated to one side, the Venerable Ānanda said this to the Blessed One - "Wonderful, Venerable Sir, marvellous, Venerable Sir! How short-lived indeed, Venerable Sir, was the Blessed One's mother; when the Blessed One was seven days old, the Blessed One's mother died and was reborn in the Tusita realm."

"So it is, Ānanda, short-lived indeed, Ānanda, are the mothers of Bodhisattas. When the Bodhisattas are seven days old, the mothers of Bodhisattas die and are reborn in the Tusita realm."

Then the Blessed One, having understood this matter, at that time uttered this inspired utterance -