Shiva Purana
सैषा पञ्चाक्षरी विद्या सर्वश्रुतिशिरोगता ॥ सर्वजातस्य सर्वस्य बीजभूता सनातनी ॥ ३९ ॥
This five-syllabled lore is present in all Upaniṣads. It is eternal as well as the seed of all living beings.
english translation
saiSA paJcAkSarI vidyA sarvazrutizirogatA ॥ sarvajAtasya sarvasya bIjabhUtA sanAtanI ॥ 39 ॥
hk transliteration by Sanscript