ŚVETĀŚVATARA UPANISHAD · 3.11
सर्वाननशिरोग्रीवः सर्वभूतगुहाशयः ।
सर्वव्यापी स भगवांस् तस्मात् सर्वगतः शिवः ॥
sarvānanaśirogrīvaḥ sarvabhūtaguhāśayaḥ ।
sarvavyāpī sa bhagavāṃs tasmāt sarvagataḥ śivaḥ ॥
That Bhagavat exists in the faces, the heads, the necks of all, he dwells in the cave (of the heart) of all beings, he is all-pervading, therefore he is the omnipresent Siva.
F. Max Müller · The Upanishads, Sacred Books of the East 15 (1884)