At Sāvatthi.
“Bhikkhus, just as households with many women but few men are easily overwhelmed by thieves and burglars, so too, a bhikkhu whose |release of mind::mental liberation, emancipation of heart, a meditation attainment [cetovimutti]| through loving-kindness is undeveloped and uncultivated is easily overwhelmed by |non-human beings::deity, god, daemon, ghost [amanussa]|. Conversely, just as households with few women but many men are hard to overcome by thieves and burglars, so too, a bhikkhu whose release of mind through loving-kindness is well-developed and cultivated is hard to overcome by non-human beings.
Therefore, bhikkhus, you should train yourselves thus: ‘Our release of mind through loving-kindness will be developed, practiced often, made a vehicle, made a basis, firmly established, nurtured, and |resolutely undertaken::fully engaged with, energetically taken up [susamāraddha]|.’ Thus, bhikkhus, you should train yourselves.”