B.G 2.26

अथ चैनं नित्यजातं नित्यं वा मन्यसे मृतम्। तथापि त्वं महाबाहो नैनं शोचितुमर्हसि ॥२-२६॥

atha cainaṁ nityajātaṁ nityaṁ vā manyase mr̥tam। tathāpi tvaṁ mahābāho nainaṁ śocitumarhasi ॥2-26॥

[ अथ च एनं नित्य जातं नित्यं वा मन्यसे मृतम्। तथा अपि त्वं महाबाहो न एनं शोचितुम् अर्हसि ॥
atha therefore; ca = and; enaṁ = this soul; nitya jātaṁ = inevitably born; nityaṁ = inevitably; vā = either; manyase = believe; mr̥tam = to be dead; tathā api = even then; tvaṁ = you; mahābāho = O mighty armed; na = not; enaṁ = this way; śocitum = to think; arhasi = you are eligiable;]

O mighty armed, even if you regard the being as inevitably born, and inevitably dying, it is not right for you to grieve.

Gīta Bhāshya 2.26

Birth and death are inevitable and hence there is no need to lament.

अस्त्वेवं आत्मनो नित्यत्वम् तथापि देहसंयोग वियोगात्मकजनिमृती स्त एव इत्यत आह "अथ च" इति ॥२६॥

astvevaṁ ātmano nityatvam tathāpi dehasaṁyoga viyogātmakajanimr̥tī sta eva ityata āha "atha ca" iti ॥26॥

[astvevaṁ ātmano nityatvam = though everlasting quality for the Jiva exists; tathāpi = even then; dehasaṁyoga viyogātmakajanimr̥tī = it experiences birth and death in the form of union with body and disunion; sta eva ityata āha = hence it is said; "atha ca" iti = so in "ata eva" verse;]

Even though Jiva is everlasting, it still goes through the process of being born and dying in the form of uniting and separating from the body. Hence the "atha ca" verse.

Gīta Tātparya 2.26

The word 'nityam' in this verse means 'inevitable' based on context and dictionary.

तिष्ठतु तावत् अयं विस्तारः। यावन्मोक्षं जीवस्य जन्ममरणे स्वयमेव मन्यसे ननु नियमेन। तथापि तावन्मात्रेणापि ज्ञानेन शोचितुं नार्हसि।

tiṣṭhatu tāvat ayaṁ vistāraḥ। yāvanmokṣaṁ jīvasya janmamaraṇe svayameva manyase nanu niyamena। tathāpi tāvanmātreṇāpi jñānena śocituṁ nārhasi।

[tiṣṭhatu tāvat ayaṁ vistāraḥ = wait is anyway required, all these explanations; yāvanmokṣaṁ jīvasya = for the being to obtain that liberation; janmamaraṇe svayameva manyase nanu niyamena = in deed birth and death must be experienced by law; tathāpi tāvanmātreṇāpi jñānena = even with this limited knowledge; śocituṁ nārhasi = you should not grieve;]

Despite the explanations provided so far, you must still wait to get liberated. In the meantime, birth and death are both subject to the law and unavoidable. With this minimal knowledge, it is clear that grieving is not worth it.

"नित्यं सनातनं प्रोक्तं नित्यं नियतमेव च"। इति शब्दनिर्णये।

"nityaṁ sanātanaṁ proktaṁ nityaṁ niyatameva ca"। iti śabdanirṇaye।

[nityaṁ = the word 'nitya'; sanātanaṁ proktaṁ = means that which is eternal; nityaṁ = the word 'nitya'; niyatameva ca = also means that which cannot be avoided; iti śabdanirṇaye = it is stated in "shabdanirnaya" dictionary;]

'The word 'nitya'means that which is eternal. It also means that which cannot be avoided" - states "shabdanirnaya" dictionary.

अत्र तु नियतम्। "जातस्य हि ध्रुवः" इति प्रकाशनात् ॥२६॥

atra tu niyatam। "jātasya hi dhruvaḥ" iti prakāśanāt ॥26॥

[atra tu niyatam = in this verse 'nitya' word should be interpreted as that which is inevitable; "jātasya hi dhruvaḥ" iti prakāśanāt = becuase is the next verse "jātasya hi dhruvaḥ", a similar meaning is expressed using the word "dhruvaḥ";]

The word 'nitya' should be interpreted as that which is inevitable. Because is the next verse "jātasya hi dhruvaḥ", a similar meaning is expressed using the word "dhruvaḥ".