Practice of 4 Brahmavihara


Another sutta connected with BV, which states that, if a person thinks they have developed BV and yet still get obsessed by ill-will, thoughts of harming, or is discontent etc, then they have not actually developed it.

Development or the developed BV, in this context, is the ability to discern the BV at will, whenever one wants, so to speak.
One might have felt great kindness, which is nice, but the BV are dwellings that one can abide in at will, they are developments of mind, not intense emotions.
If one were to have that developed state, then the mere finger snap of entering that dwelling once it is built is infinitely meritorious. It was developed, one knows it, and can return to it, and abide for quite a few more finger snaps.