Shiva Purana

siva.sh/siva-purana/saturda-samhita/2/12

आत्मा तस्याष्टमं रूपं शिवस्य परमात्मनः ।। व्यापिकेतरमूर्तीनां विश्वं तस्माच्छिवात्मकम् ।। १२ ।।

sanskrit

The eighth form of Śiva, the great soul, is the Ātman, more pervasive than the other forms. The universe is pervaded by that form.

english translation

AtmA tasyASTamaM rUpaM zivasya paramAtmanaH || vyApiketaramUrtInAM vizvaM tasmAcchivAtmakam || 12 ||

hk transliteration by Sanscript