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.