Mundaka 4.14
ब्रह्मैवेदममृतं पुरस्ताद् ब्रह्म पश्चाद् ब्रह्म दक्षिणतश्चोत्तरेण। अधश्चोर्ध्वं च प्रसृतं ब्रह्मैवेदं विश्वमिदं वरिष्ठम् ॥१४॥
Brahman is the immortal essence present everywhere: in front, behind, to the south, to the north, below, and above. This entire universe is indeed the Brahman; this Brahman is indeed supreme.
Bhāshya 4.14
The word 'idam' is used in various contexts, but here it specifically refers to Brahman due to its multiplicity of meanings.
इदं ब्रह्मैव विश्वं पूर्णम्। इदमेव वरिष्ठं सर्वोत्तमम्। इदंशब्दानां बहुत्वाद् ब्रह्मविषय एवेदंशब्दः ॥
This universe is indeed Brahman, and thus complete in itself. This alone is the greatest and the best. The word 'idam' is used in various contexts, but here it specifically refers to Brahman due to its multiplicity of meanings.
॥ इति चतुर्थः खण्डः ॥
This marks the end of the fourth section.