The Mukhya Upaniṣads

Maitrī · Prapāṭhaka 2 · Maitrī 2.1

Passage 2

य एषो बाह्यावष्टम्भनेनोर्ध्वमुत्क्रान्तो व्यथमानोऽव्यथमानस्तमः प्रणुदत्येष आत्मेत्याह भगवानथ य एष संप्रसादोऽस्माञ्छरीरात्समुत्थाय परं ज्योतिरुपसंपद्य स्वेन रूपेणाभिनिष्पद्यत एष आत्मेति होवाचैतदमृतमभयमेतद्ब्रह्मेति ॥२.२ ॥

In plain words

That which, when the outward support is withdrawn, goes upward without trembling, though it seems to tremble, and drives away the darkness — that is the Self, said the blessed one. And that serene one who, rising out of this body and reaching the highest light, comes forth in his own form — that is the Self, he said. That is the immortal, the fearless; that is Brahman.