4.
The Discourse on the Pure
390.
At Sāvatthī.
"Monks, there are these four establishments of mindfulness.
Which four?
Here, monks, a monk dwells observing the body in the body, ardent, fully aware, mindful, having removed covetousness and displeasure regarding the world;
in feelings... etc.
In mind... etc.
He dwells observing mental phenomena in mental phenomena, ardent, fully aware, mindful, having removed covetousness and displeasure regarding the world.
These, monks, are the four establishments of mindfulness."
The fourth.