In the first passage "nibbānāya
" is indeed a dative. Dative is usually explained with the help of the phrase "I give to [a word in dative]". So in the quoted Pāli text above it is "to the Nibbāna
". Dative is usually used when we talk about a destination, a goal (see S. Collins "Pāli grammar"), like in the "First Sermon": "majjhimā paṭipadā... cakkhukaraṇī ñāṇakaraṇī upasamāya abhiññāya sambodhāya nibbānāya saṃvattati
" ("the middle practice/way, that leads to..."). The verb saṃvattati
("to lead (to)") requires a dative here, as what is implied is movement
from the point A to the point B. So the translation of the passage is quite correct.
While in your second passage, "anātāpī anottappī abhabbo sambodhāya abhabbo nibbānāya
" and "nibbānāya
" are rare "possesive datives" (or, simply, genitives), i.e. "of...": anātāpī
(Nom. "a not ardent one") + anottappī
(Nom. "a reckless one") + abhabbo
(adj. [are], "unable/impossible/uncapable") + (Gen. "of Enlightenment, of Nibbāna
O. H. de A. Wijesekera understands it as the Dative of Suitability.
§108. The Dat. of Suitability.
The dat. is also found with verbs, nouns (including adjectives) and particles (originally adverbs or prepositions) having the sense of befitting, suiting and counterpoising (cp. SS §87). Such are the verbs kappati and pahoti (cp. Pāṇ. II.2.13 & 2.16), nouns like kālo, akālo, adjectives of the sense of paṭirūpa and prepositions like alaṃ.
e. With some adjectives denoting competency or possibility a similar dat. is found in the Nikāyas, used very much like the dat. (or even the gen.) in Skr. with words like paryāpta and  śakta (SS §85). e.g., bhabbo “possible, fit”;
bhabbo abhinibbidāya, bhabbo sambodhāya M I.104
“has the capacity for breaking away (from the world) and for enlightenment”;
bhabbo dukkhakkhayāya S III.27
“has the capacity for destroying ill”;
abhabbo puna virūḷhiyā M II.256
“impossible to grow again”;
abhabbo parihānāya A II.40
“unlikely to decrease”.
With these the infinitive is also found showing that it is an infinitival dat. of the type discussed above (vide P.T.S. Dict, s.v.)
https://www.ancient-buddhist-texts.net/ ... .htm#toc19
is surely synonymous with nibbānā
, in the later Sarvāstivāda scholasticism the term pratisaṃkhyā-nirodha
became the main term for nirvāṇa
, instead of nirvāṇa
. (see ven.Dhammajoti, Sarvāstivāda Abhidharma. 2009. p. 471).
in the formulas such as yours is explained as: "not to the stoppage of non-being of passion etc." (Na nirodhāyāti na rāgādīnaṃ appavattinirodhāya
, from the commentary to the line from the Anuttariyasutta
, PTS III 325). "Dukkhanirodhāya" I don't find as well, but it is implied by the "taṇhānirodhāya", as taṇhā
is many times explained to be dukkha