Verse 5.17.1

अथ होवाचोद्दालकमारुणिं गौतम कं त्वमात्मानमुपस्स इति पृथिवीमेव भगवो राजन्निति होवाचैष वै प्रतिष्ठात्मा वैश्वानरो यं त्वमात्मानमुपास्से तस्मात्त्वं प्रतिष्ठितोऽसि प्रजया च पशुभिश्च ॥ ५.१७.१ ॥

atha hovācoddālakamāruṇiṃ gautama kaṃ tvamātmānamupassa iti pṛthivīmeva bhagavo rājanniti hovācaiṣa vai pratiṣṭhātmā vaiśvānaro yaṃ tvamātmānamupāsse tasmāttvaṃ pratiṣṭhito'si prajayā ca paśubhiśca || 5.17.1 ||

1. The king then said to Uddālaka Āruṇi, ‘O Gautama, whom do you worship as the Self?’ Uddālaka replied, ‘I worship the earth, revered king.’ The king said: ‘That which you worship as the Vaiśvānara Ātman is named Pratiṣṭhā [the support]. This is why you have so many children and animals to support you’.

Word-for-word explanation:

Atha, next; ha uvāca, he [the king] said; uddālakam āruṇim, to Uddālaka Āruṇi; gautama, O Gautama; kam, whom; tvam ātmānam upāsse iti, do you worship as the Self; bhagavaḥ rājan, revered king; pṛthivīm eva iti, [I worship] the earth; ha uvāca, [the king] said; yam tvam ātmānam upāsse, the Self which you worship; eṣaḥ, this [earth]; vai, for sure; ātmā vaiśvānaraḥ, is the Vaiśvānara Ātman; pratiṣṭhā, as Pratiṣṭhā [the support]; tasmāt, therefore; tvam, you; pratiṣṭhitaḥ prajayā ca paśubhiḥ ca asi, are supported by children and animals.

Commentary:

The earth is like the feet of Vaiśvānara Ātman. This is why it is ‘the support.’