And what is right mindfulness? It’s when a mendicant meditates by observing an aspect of the body—keen, aware, and mindful, rid of covetousness and displeasure for the world. They meditate observing an aspect of feelings … mind … principles—keen, aware, and mindful, rid of covetousness and displeasure for the world. This is called right mindfulness.

And what is right immersion? It’s when a mendicant, quite secluded from sensual pleasures, secluded from unskillful qualities, enters and remains in the first absorption, which has the rapture and bliss born of seclusion, while placing the mind and keeping it connected. As the placing of the mind and keeping it connected are stilled, they enter and remain in the second absorption, which has the rapture and bliss born of immersion, with internal clarity and mind at one, without placing the mind and keeping it connected. And with the fading away of rapture, they enter and remain in the third absorption, where they meditate with equanimity, mindful and aware, experiencing for themselves the bliss of which the noble ones declare, ‘Equanimous and mindful, one meditates in bliss.’ With the giving up of pleasure and pain and the disappearance of former happiness and sadness, they enter and remain in the fourth absorption, without pleasure or pain, with pure equanimity and mindfulness. This is called right immersion. This is called the noble truth of the practice that leads to the cessation of suffering.

Near Varanasi, in the deer park at Isipatana, the Realized One, the perfected one, the fully awakened Buddha rolled forth the supreme Wheel of Dhamma. And that wheel cannot be rolled back by any ascetic or brahmin or god or Māra or divinity or by anyone in the world. It is the teaching, advocating, establishing, clarifying, analyzing, and revealing of the four noble truths.” That is what Venerable Sāriputta said. Satisfied, the mendicants approved what Sāriputta said.

Middle Discourses 142 The Analysis of Religious Donations