BṚHADĀRAṆYAKA UPANISHAD · 5.1.1

पूर्णम् अदः पूर्णम् इदं पूर्णात् पूर्णम् उदच्यते ।
पूर्णस्य पूर्णम् आदाय पूर्णम् एवावशिष्यते ।
खं ब्रह्म ।
खं पुराणम् ।
वायुरं खम् ।
इति ह स्माह कौरव्यायणीपुत्रः ।
वेदो ऽयं ब्राह्मणा विदुः ।
वेदैनेन यद् वेदितव्यम् ॥

pūrṇam adaḥ pūrṇam idaṃ pūrṇāt pūrṇam udacyate ।
pūrṇasya pūrṇam ādāya pūrṇam evāvaśiṣyate ।
khaṃ brahma ।
khaṃ purāṇam ।
vāyuraṃ kham ।
iti ha smāha kauravyāyaṇīputraḥ ।
vedo ’yaṃ brāhmaṇā viduḥ ।
vedainena yad veditavyam ॥

That (the invisible Brahman) is full, this (the visible Brahman) is full. This full (visible Brahman) proceeds from that full (invisible Brahman). On grasping the fulness of this full (visible Brahman) there is left that full (invisible Brahman). Om (is) ether, (is) Brahman. 'There is the old ether (the invisible), and the (visible) ether of the atmosphere,' thus said Kauravyâyanîputra. This (the Om) is the Veda (the means of knowledge), thus the Brâhmanas know. One knows through it all that has to be known.

F. Max Müller · The Upanishads, Sacred Books of the East 15 (1884)