SN 56.20  Tatha sutta - True

“Cattārimāni, bhikkhave, tathāni avitathāni anaññathāni. Katamāni cattāri? ‘Idaṁ dukkhan’ti, bhikkhave, tathametaṁ avitathametaṁ anaññathametaṁ; ‘ayaṁ dukkhasamudayo’ti tathametaṁ avitathametaṁ anaññathametaṁ; ‘ayaṁ dukkhanirodho’ti tathametaṁ avitathametaṁ anaññathametaṁ; ‘ayaṁ dukkhanirodhagāminī paṭipadā’ti tathametaṁ avitathametaṁ anaññathametaṁ— imāni kho, bhikkhave, cattāri tathāni avitathāni anaññathāni.

“These four things, bhikkhus, are true, unerring, and not otherwise. What four? ‘This is |suffering::discomfort, unpleasantness, discontentment, dissatisfaction, stress, pain, disease, i.e. mild or intense suffering [dukkha]|,’ bhikkhus, this is true, this is unerring, this is not otherwise; ‘This is the |arising of suffering::source of stress, appearance of discomfort [dukkhasamudaya]|,’ this is true, this is unerring, this is not otherwise; ‘This is the |end of suffering::ending of discontentment, cessation of distress [dukkhanirodha]|,’ this is true, this is unerring, this is not otherwise; ‘This is the |way of practice leading to the end of suffering::i.e. the Noble Eightfold Path consisting of right view, right intention, right speech, right action, right livelihood, right effort, right mindfulness, and right collectedness [dukkhanirodhagāmī]|,’ this is true, this is unerring, this is not otherwise. These, bhikkhus, are the four truths that are true, unerring, and not otherwise.

Tasmātiha, bhikkhave, ‘idaṁ dukkhan’ti yogo karaṇīyo,
‘ayaṁ dukkhasamudayo’ti yogo karaṇīyo,
‘ayaṁ dukkhanirodho’ti yogo karaṇīyo,
‘ayaṁ dukkhanirodhagāminī paṭipadā’ti yogo karaṇīyo”ti.

Therefore, bhikkhus, effort should be made to |fully understand::understand in principle, then discern in each moment and then experientially penetrate|: ‘This is suffering’;
effort should be made to fully understand: ‘This is the arising of suffering’;
effort should be made to fully understand: ‘This is the end of suffering’;
effort should be made to fully understand: ‘This is the way of practice leading to the end of suffering.’”