Bhāvanā sutta: Development

“Mendicants, I will teach you the development of the four kinds of mindfulness meditation. Listen …

And what is the development of the four kinds of mindfulness meditation? 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 the development of the four kinds of mindfulness meditation.”