Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 12
Sanskrit:
नश्वरेष्विह भावेषु तदसि त्वमनश्वरम् ।यथा द्रव्यविकारेषु द्रव्यमात्रं निरूपितम् ॥ १२ ॥
ITRANS:
naśvareṣv iha bhāveṣutad asi tvam anaśvaramyathā dravya-vikāreṣudravya-mātraṁ nirūpitam
Translation:
You are the one indestructible entity among all the destructible things of this world, like the underlying substance that is seen to remain unchanged while the things made from it undergo transformations.