The Buddha reviews the multitude of harmful and unwholesome mental qualities he has abandoned, and the multitude of wholesome mental qualities he has developed to completion.
Evaṁ me sutaṁ— ekaṁ samayaṁ bhagavā sāvatthiyaṁ viharati jetavane anāthapiṇḍikassa ārāme. Tena kho pana samayena bhagavā attano aneke pāpake akusale dhamme pahīne paccavekkhamāno nisinno hoti, aneke ca kusale dhamme bhāvanāpāripūriṁ gate.
Thus have I heard—At one time, the Blessed One was dwelling at Sāvatthi, in Jeta’s grove, Anāthapiṇḍika’s park. Now, at that time, the Blessed One was sitting, |reviewing::reviewing on, looking at [paccavekkhamāna]| the multitude of |harmful::injurious, destructive, bad, or evil [pāpaka]| and |unwholesome::unhealthy, unskillful, unbeneficial, or karmically unprofitable [akusala]| mental qualities he had abandoned, and the multitude of |wholesome::healthy, beneficial, useful [kusala]| mental qualities that he had |developed to completion::cultivated to maturity [bhāvanāpāripūri]|.
Atha kho bhagavā attano aneke pāpake akusale dhamme pahīne viditvā aneke ca kusale dhamme bhāvanāpāripūriṁ gate tāyaṁ velāyaṁ imaṁ udānaṁ udānesi:
Then the Blessed One, having perceived that multitude of harmful and unwholesome qualities had been abandoned by him, and that multitude of wholesome qualities had been developed to completion, at that time uttered this inspired utterance:
“Ahu pubbe tadā nāhu,
nāhu pubbe tadā ahu;
Na cāhu na ca bhavissati,
na cetarahi vijjatī”ti. [1]
“There was in the past, then there was not,
there was not in the past, then there was;
It neither was, nor will it be,
nor does it exist |now::at present [cetarahi]|.” [1]
Thus have I heard—At one time, the Blessed One was dwelling at Sāvatthi, in Jeta’s grove, Anāthapiṇḍika’s park. Now, at that time, the Blessed One was sitting, |reviewing::reviewing on, looking at [paccavekkhamāna]| the multitude of |harmful::injurious, destructive, bad, or evil [pāpaka]| and |unwholesome::unhealthy, unskillful, unbeneficial, or karmically unprofitable [akusala]| mental qualities he had abandoned, and the multitude of |wholesome::healthy, beneficial, useful [kusala]| mental qualities that he had |developed to completion::cultivated to maturity [bhāvanāpāripūri]|.
Then the Blessed One, having perceived that multitude of harmful and unwholesome qualities had been abandoned by him, and that multitude of wholesome qualities had been developed to completion, at that time uttered this inspired utterance:
“There was in the past, then there was not,
there was not in the past, then there was;
It neither was, nor will it be,
nor does it exist |now::at present [cetarahi]|.” [1]
Evaṁ me sutaṁ— ekaṁ samayaṁ bhagavā sāvatthiyaṁ viharati jetavane anāthapiṇḍikassa ārāme. Tena kho pana samayena bhagavā attano aneke pāpake akusale dhamme pahīne paccavekkhamāno nisinno hoti, aneke ca kusale dhamme bhāvanāpāripūriṁ gate.
Atha kho bhagavā attano aneke pāpake akusale dhamme pahīne viditvā aneke ca kusale dhamme bhāvanāpāripūriṁ gate tāyaṁ velāyaṁ imaṁ udānaṁ udānesi:
“Ahu pubbe tadā nāhu,
nāhu pubbe tadā ahu;
Na cāhu na ca bhavissati,
na cetarahi vijjatī”ti. [1]
[1] I suspect that the verse refers to a review of harmful and unwholesome mental qualities done one at a time. This process is to show that an awakened being carefully examines and verifies things as they have come to be instead of assuming or jumping to conclusions.