The works of Ādi Śaṅkarācārya

Sanatsujātīyam

p. 230

p. 230

ते दुर्धर्षा दुष्प्रकम्प्या विद्याच्छान्तान्ब्रह्मणस्तनुम् ॥

In plain words

No one can overpower them, no one can make them waver. Know the quiet ones as the very body Brahman wears.

Close to the Sanskrit

They are hard to assail, hard to shake; one should know the tranquil ones as the body of Brahman.