B.G 2.22
वासांसि जीर्णानि यथा विहाय नवानि गृह्णाति नरोऽपराणि। तथा शरीराणि विहाय जीर्णान्यन्यानि संयाति नवानि देही ॥ २-२२॥
vāsāṁsi jīrṇāni yathā vihāya navāni gr̥hṇāti narō'parāṇi। tathā śarīrāṇi vihāya jīrṇānyanyāni saṁyāti navāni dēhī ॥ 2-22॥
Just as a person casts off worn-out clothes and puts on new ones, similarly the being gives up worn-out bodies and takes up other bodies that are new.
Gīta Bhāshya 2.22
Discriminative knowledge between the body and the soul and its experiential knowledge is imparted.
To impart discriminative and experiential knowledge of the body and the soul, a metaphor is provided in the above 'vāsāṁsi' verse.
Gīta Tātparya 2.22
Union and separation of the body from the soul is birth and death, respectively. There is no need to grieve for the same.
Even jīva has union and separation with the body in the form of birth and death. The verse 'vāsāṁsīti' clarifies that it should not be the reason to grieve.