Bhagavad Gita 10.20

अहमात्मा गुडाकेश सर्वभूतशयस्थित: |
अहमादिश्च मध्यं च भूतानामन्त एव च

Translation

O Arjun, I am seated in the heart of all living entities. I am the beginning, middle, and end of all beings.