The Brahma Vihārās – often translated as the divine or sublime abodes, or as the four immeasurables – can be used to focus for meditative inquiry. They are:
- loving kindness – maitrī / mettā
- talks and readings on mettā, including the Buddha’s words on loving kindness
- compassion – karuṇā
- empathetic joy – muditā
- equanimity – upekṣā / upekkhā
Here’s a short essay by Robert Aitken Roshi on Zen practice and the Brahma Vihārās – published in Original dwelling place: Zen Buddhist essays.
And here is a 10 minute introduction to the Brahma Vihārās and Zen, by Kirk, from late 2021 –