Mandukya Karika, verse 1.28

Text

प्रणवं हीश्वरं विद्यात्सर्वस्य हृदि संस्थितम् ।
सर्वव्यापिनमोंकारं मत्वा धीरो न शोचति ॥ २८ ॥

praṇavaṃ hīśvaraṃ vidyātsarvasya hṛdi saṃsthitam |
sarvavyāpinamoṃkāraṃ matvā dhīro na śocati || 28 ||

28. Know Aum to be Īśvara, ever present in the mind of all; the man of discrimination realising Aum as all-pervading, does not grieve.

Shankara Bhashya (commentary)

Know Aum as the Īśvara present in the mind, which is the seat1 of memory and perception, of all things. The man of discrimination realising Aumkāra as all-pervading2 like the sky, i.e., knowing it as the Ātman, not bound by the law of transmigration, does not grieve; for, there is no cause3 of misery for him. The Scriptures also abound in such passages as, “The knower of Ātman goes beyond grief.”