tatiyaṃ jhānaṃ upasampajja viharati = he attains and lives in third jhāna.
3rd jhāna misc.
Essence of j3🌖 third Jhāna
* When one is first learning jhānas, first and second jhāna can have strong emotional thrill and excitement.
* On the mental development side of third jhāna, compared to second, we focus on the skill dispassion towards pīti (mental joy).
* Why? Pīti requires an energetic expenditure to fabricate intentions to produce mental joy.
When one already knows how to flip the switch to enter jhāna that is born of samādhi (second jhāna or higher),
one need not expend extraneous energy getting excited about it.
Just like an elite athlete who scores winning plays doesn’t need wild emotional energy expending overt displays of celebration, he calmly goes on in a state of upekkha.
Making winning plays is just expected and normal for him, so he saves his energy for more important Dharmas.
* upekkha, equanimous-observation, becomes prominent in third jhāna. In passive mode, upekkha and sampajāno equanimously observes the experience of pleasant abiding.
In dynamic mode, upekkha and sampajāno investigates the Dharma, for example seeing dukkha and its cause.