[725] Therein, what is the fourth jhāna?
Here, on the occasion when a bhikkhu develops supramundane (lokuttara) jhāna — leading out [of the round] (niyyānika), going to the dismantling [of existence] (apacayagāmī) — for the abandoning of views (diṭṭhigata), for the attainment of the first plane (bhūmi), and, with the abandoning of pleasure … he enters upon and dwells in the fourth jhāna, of painful practice and sluggish direct knowledge (dukkhāpaṭipadā dandhābhiññā): on that occasion there is two-factored (duvaṅgika) jhāna — equanimity (upekkhā) and one-pointedness of mind (cittassa ekaggatā). This is called the fourth jhāna. The remaining phenomena (dhammā) are associated with the jhāna.
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.