At Sāvatthī.

“Mendicants, there are these four kinds of mindfulness meditation. What four? It’s when a mendicant meditates by observing an aspect of the body—keen, aware, and mindful, rid of desire and aversion for the world. They meditate observing an aspect of feelings … mind … principles—keen, aware, and mindful, rid of desire and aversion for the world.

These are the four kinds of mindfulness meditation.”