THUS HAVE I HEARD 

On one occasion the Blessed One was living at Sāvatthī in Jeta’s Grove, Anāthapiṇḍika’s Park.

There he addressed the bhikkhus thus: “Bhikkhus.” — “Venerable sir,” they replied. The Blessed One said this:

“Bhikkhus, I shall teach you the summary and exposition of ‘One Who Has Had a Single Excellent Night.’ Listen and attend closely to what I shall say.” 

- “Yes, venerable sir,” the bhikkhus replied. The Blessed One said this:

“Let not a person revive the past
Or on the future build his hopes
For the past has been left behind
And the future has not been reached.

Instead with insight let him see
Each presently arisen state
Let him know that and be sure of it,
Invincibly, unshakeably.

Today the effort must be made;
Tomorrow Death may come, who knows?
No bargain with Mortality
Can keep him and his hordes away,

But one who dwells thus ardently,
Relentlessly, by day, by night —
It is he, the Peaceful Sage has said,
Who has had a single excellent night.

“How, bhikkhus, does one revive the past?
One nurtures delight there thinking, ‘I had such material form in the past.’
One nurtures delight there thinking, ‘I had such feeling in the past,’…
‘I had such perception in the past,’…
‘I had such formations in the past,’…
‘I had such consciousness in the past.’
That is how one revives the past.