देहिनोऽस्मिन्यथा देहे कौमारं यौवनं जरा।
तथा देहान्तरप्राप्तिर्धीरस्तत्र न मुह्यति।।2.13।।
2.13 As are boyhood, youth and decrepitude to an embodied being in this (present) body, similar is the acisition of another body. This being so, an intelligent person does not get deluded.
2.13 As the self is eternal, one does not grieve, thinking that the self is lost, when an embodied self living in a body gives up the state of childhood and attains youth and other states. Similarly, the wise men, knowing that the self is eternal, do not grieve, when the self attains a body different from the present body. Hence the selves, being eternal, are not fit objects for grief. This much has to be done here; the eternal selves because of Their being subject ot beginningless Karma become endowed with bodies suited to Their Karmas. To get rid of this bondage (of bodies), embodied beings perform duties like war appropriate to their stations in life with the help of the same bodies in an attitude of detachment from the fruits as prescribed by the scripture. Even to such aspirants, contacts with sense-objects give pleasure and pain, arising from cold, heat and such other things. But these experiences are to be endured till the acts enjoined in the scriptures come to an end. The Lord explains the significance immediately afterwards:
Dehino’smin yathaa dehe kaumaaram yauvanam jaraa; Tathaa dehaantara praaptir dheeras tatra na muhyati.
dehinaḥ—of the embodied; asmin—in this; yathā—as; dehe—in the body; kaumāram—childhood; yauvanam—youth; jarā—old age; tathā—similarly; deha-antara—another body; prāptiḥ—achieves; dhīraḥ—the wise; tatra—thereupon; na muhyati—are not deluded