Chapter 2 · The Yoga of Knowledge · Krishna said
Bhagavad Gita 2.13 — Changing bodies
देहिनोऽस्मिन्यथा देहे कौमारं यौवनं जरा। तथा देहान्तरप्राप्तिर्धीरस्तत्र न मुह्यति ॥
dehino'sminyathā dehe kaumāraṃ yauvanaṃ jarā | tathā dehāntaraprāptirdhīrastatra na muhyati ||
Meaning
Just as the soul in this body passes through childhood, youth and old age, so it passes into another body. The wise are not confused by this.