Bhagavad Gita 10.15
You alone know Yourself, by the power of Your Self; You are the Supreme Spirit, the Source and Master of all being, the Lord of Lords, the Ruler of the Universe.
स्वयमेवात्मनाऽत्मानं वेत्थ त्वं पुरुषोत्तम।
भूतभावन भूतेश देवदेव जगत्पते॥svayamevātmanā'tmānaṃ vettha tvaṃ puruṣottama|
bhūtabhāvana bhūteśa devadeva jagatpate||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).