Bhagavad Gita Chapter 10.20
aham ātmā guḍākeśa
sarva-bhūtāśaya-sthitaḥ
aham ādiś ca madhyaḿ ca
bhūtānām anta eva ca
Translation
I am the Supersoul, O Arjuna, seated in the hearts of all living entities. I am the beginning, the middle and the end of all beings.