Paṭisallānasutta
“Paṭisallāne, bhikkhave, yogamāpajjatha. Paṭisallīno, bhikkhave, bhikkhu yathābhūtaṁ pajānāti. Kiñca yathābhūtaṁ pajānāti? ‘Cakkhu aniccan’ti yathābhūtaṁ pajānāti; ‘rūpā aniccā’ti yathābhūtaṁ pajānāti; ‘cakkhuviññāṇaṁ aniccan’ti yathābhūtaṁ pajānāti; ‘cakkhusamphasso anicco’ti yathābhūtaṁ pajānāti …pe… ‘yampidaṁ manosamphassapaccayā uppajjati vedayitaṁ sukhaṁ vā dukkhaṁ vā adukkhamasukhaṁ vā tampi aniccan’ti yathābhūtaṁ pajānāti. Paṭisallāne, bhikkhave, yogamāpajjatha. Paṭisallīno, bhikkhave, bhikkhu yathābhūtaṁ pajānātī”ti.
Retreat
“Mendicants, meditate in retreat. A mendicant in retreat truly understands. What do they truly understand? They truly understand that the eye is impermanent. They truly understand that sights … eye consciousness … eye contact … the pleasant, painful, or neutral feeling that arises dependent on mind contact is impermanent. Mendicants, meditate in retreat. A mendicant in retreat truly understands.”