BhG 18.54

syntax

brahma-bhūtaḥ (being Brahman) prasannātmā (of a joyful self) na śocati (he does not lament) na kāṅkṣati [ca] (and does not desire).
[saḥ] (he) sarveṣu bhūteṣu (towards all beings) samaḥ (the same) parām mad-bhaktim (supreme devotion for me) labhate (he obtains).

grammar

brahma-bhūtaḥ	–	brahma-bhūta 1n.1 m..; TP: brahmaṇi bhūta iti – being in brahman / being brahman (from: √bṛh – to increase, brahman – spirit, the Vedas; √bhū – to be, PP bhūta – been, real, world);
prasannātmā	–	prasanna-ātman 1n.1 m.; BV: yasyātmā prasanno ‘sti saḥ – whose self is pleased (from: pra-√sad – to settle down, to be pleased, to be successful, PP prasanna – clear, pleased, soothed; ātman – self);
na	–	av. – not;
śocati	–	√śuc (to lament, to bewail) Praes. P 1v.1 – he laments;
na	–	av. – not;
kāṅkṣati	–	√kāṅkṣ (to desire, to expect) Praes. P 1v.1 – he desires;
samaḥ	–	sama sn. 1n.1 n. – the same, equal, equivalent;
sarveṣu	–	sarva sn. 7n.3 m. loc.abs. – in all;
bhūteṣu	–	bhūta (√bhū – to be) PP 7n.3 m. loc.abs. – in beings;
mad-bhaktim	–	mad-bhakti 2n.1 f.; TP: mama bhaktim iti – devotion for me (from: mat – the basic form of a personal ponoun „I” singular used in compounds; √bhaj – to share, to love, to rejoice, to worship, bhakti – devotion, love, fondness);
labhate	–	√labh (to obtain) Praes. Ā 1v.1 – he obtains;
parām	–	para 2n.1 f. – beyond, ancient, final, the best, the supreme;

textual variants

kāṅkṣati → hṛṣyati (he excites);
parām → naraḥ (a person);

The second pada of verse 18.54 is the same as the second pada of verse BhG 12.17;

Śāṃkara

anena krameṇa—
brahma-bhūto brahma-prāptaḥ prasannātmā labdhādhyātma-prasāda-svabhāvo na śocati, kiṃcit artha-vaikalyam, ātmano vaiguṇyaṃ vā uddiśya na śocati na santapyate | na kāṅkṣati, na hy aprāpta-viṣayākāṅkṣā brahma-vida upapadyate | ato brahma-bhūtasyāyaṃ svabhāvo’nūdyate—na śocati na kāṅkṣatīti | na hṛṣyatīti vā pāṭhāntaram | samaḥ sarveṣu bhūteṣu, ātmaupamyena sarva-bhūteṣu sukhaṃ duḥkhaṃ vā samam eva paśyatīty arthaḥ | nātma-sama-darśanam iha, tasya vakṣyamāṇatvāt bhaktyā mām abhijānāti [gītā 18.55] iti | evaṃ-bhūto jñāna-niṣṭhaḥ, mad-bhaktiṃ mayi parameśvare bhaktiṃ bhajanaṃ parām uttamāṃ jñāna-lakṣaṇāṃ catur thī labhate, caturvidhā bhajante mām [gītā 7.16] ity uktam

Rāmānuja

brahmabhūtaḥ āvirbhūtāparicchinnajñānaikākāramaccheṣataikasvabhāvātmasvarūpaḥ, „itas tv anyāṃ prakṛtiṃ viddhi me parām” iti hi svaśeṣatoktā / prasannātmā kleśakarmādibhir akaluṣasvarūpo madvyatiriktaṃ na kaṃcana bhūtaviśeṣaṃ prati śocati; na kiṃcana kāṅkṣati; api tu madvyatirikteṣu sarveṣu bhūteṣu anādaraṇīyatāyāṃ samo nikhilaṃ vastujātaṃ tṛṇavan manyamāno madbhaktiṃ labhate parām mayi sarveśvare nikhilajagadudbhavasthitipralayalīle nirastasamastaheyagandhe ‚navadhikātiśayāsaṃkhyeyakalyāṇaguṇagaṇaikatāne lāvaṇyāmṛtasāgare śrīmati puṇḍarīkanayane svasvāmini atyarthapriyānubhavarūpāṃ parāṃ bhaktiṃ labhate

Śrīdhara

brahmāham iti naiścalyenāvasthānasya phalam āha brahmeti | brahma-bhūto brahmaṇy avasthitaḥ prasanna-cittaḥ naṣṭaṃ na śocati na cāprāptaṃ kāṅkṣati dehādya-abhimānābhāvāt | ataeva sarveṣv api bhūteṣu samaḥ san rāga-dveṣam ādikṛta-vikṣepābhāvāt sarva-bhūteṣu mad-bhāvanā-lakṣaṇṃṃ parāṃ bhaktiṃ labhate

Viśvanātha

tataś copādhy-apagame sati brahma-bhūto ‚nāvṛtta-caitanyatvena brahma-rūpa ity arthaḥ | guṇa-mālinyāpagamāt | prasannaś cāsāv ātmā ceti saḥ | tataś ca pūrva-daśāyām iva naṣṭaṃ na śocati na cāprāptaṃ kāṅkṣati dehādy-abhimānābhāvād iti bhāvaḥ | sarveṣu bhūteṣu bhadrābhadreṣu bālaka iva samaḥ bāhyānusandhānābhāvād iti bhāvaḥ |

tataś ca nirindhanāgnāv iva jñāne śānte ‚py anaśvarāṃ jñānāntarbhūtāṃ mad-bhaktiṃ śravaṇa-kīrtanādi-rūpāṃ labhate | tasyā mat-svarūpa-śakti-vṛttitvena māyā-śakti-bhinnatvād avidyāvidyayor apagame ‚py anapagamāt | ataeva parāṃ jñānād anyāṃ śreṣṭhāṃ niṣkāma-karma-jñānādy-urvaritatvena kevalām ity arthaḥ | labhata iti pūrvaṃ jñāna-vairāgyādiṣu mokṣa-siddhy-arthaṃ kalayā vartamānāyā api sarva-bhūteṣv antaryāmina iva tasyāḥ spaṣṭopalabdhir nāsīd iti bhāvaḥ | ataeva kuruta ity anuktvā labhata iti prayuktam | māṣam udgādiṣu militāṃ teṣu naṣṭeṣv apy anaśvarāṃ kāñcana-maṇikām iva tebhyaḥ pṛthaktayā kevalāṃ labhata itivat | sampūrṇāyāḥ prema-bhaktes tu prāyas tadānīṃ lābha-sambhavo ‚sti nāpi tasyāḥ phalaṃ sāyujyam ity ataḥ parā-śabdena prema-lakṣaṇeti vyākhyeyam

Baladeva

tasya brahma-bhūyottara-bhāvinaṃ lābham āha brahmeti | brahma-bhūtaḥ sākṣāt-kṛtāṣṭa-guṇaka-sva-svarūpaḥ | prasannātmā kleśa-karma-vipākāśayānāṃ vigamād atisvacchaḥ – nadyaḥ prasanna-salilāḥ ity ādāv ativaimalyaṃ prasnna-śabdārthaḥ | sa evambhūto mad-anyāt kāṃścit prati na śocati na ca tān kāṅkṣati | sarveṣu mad-anyeṣūccāvaceṣu bhūteṣu samaḥ heyatvāviśeṣālloṣṭra-kāṣṭhavattvāni manyamānaḥ īdṛśaḥ san parāṃ mad-bhaktiṃ niṣṭhāṃ jñānasya yā parā ity (Gītā 18.50) uktāṃ mad-anubhava-lakṣaṇāṃ mad-vīkṣaṇa-samānākārāṃ sādhyāṃ bhaktiṃ vindatīty arthaḥ