Shiva Purana

siva.sh/siva-purana/uma-samhita/4/9

शिवस्यैव परा मूर्तिर्ब्रह्मविष्ण्वीश्वरात्मिका ।। सर्वभूतात्मभूताख्या त्रिलिंगा लिंगरूपिणी।। ९।।

sanskrit

It is the great image of Śiva that manifests as Brahmā. Viṣṇu and Śiva. It is that which has become the soul of all living beings. It is both three-symbolled and symbolless.

english translation

zivasyaiva parA mUrtirbrahmaviSNvIzvarAtmikA || sarvabhUtAtmabhUtAkhyA triliMgA liMgarUpiNI|| 9||

hk transliteration by Sanscript