Verse 5.10.6

अभ्रं भूत्वा मेघो भवति मेघो भूत्वा प्रवर्षति त इह व्रीहियवा ओषधिवनस्पतयस्तिलमाषा इति जायन्तेऽतो वै खलु दुर्निष्प्रपतरं यो यो ह्यन्नमत्ति यो रेतः सिञ्चति तद्भूय एव भवति ॥ ५.१०.६ ॥

abhraṃ bhūtvā megho bhavati megho bhūtvā pravarṣati ta iha vrīhiyavā oṣadhivanaspatayastilamāṣā iti jāyante'to vai khalu durniṣprapataraṃ yo yo hyannamatti yo retaḥ siñcati tadbhūya eva bhavati || 5.10.6 ||

6. Having become mist, it changes into clouds. Then from clouds, it becomes rain and falls to the earth. Finally it grows as paddy, barley, plants, trees, sesame, beans, and so forth. The change from this state is very difficult. Those who eat these things produce children just like themselves.

Word-for-word explanation:

Abhram bhūtvā meghaḥ bhavati, having become mist, it becomes a cloud; meghaḥ bhūtvā pravarṣati, having become a cloud, it comes down as rain; te, they; iha, in this world; vrīhi-yavāḥ, paddy and barley; oṣadhi-vanaspatayaḥ, plants and trees; tila-māṣaḥ iti, sesame, beans, and so forth; jāyante, this.is how they are born; ataḥ, from this [state]; vai khalu, for sure; durniṣprapataram, the way is difficult; yaḥ yaḥ, whoever [humans or animals]; hi annam atti, eats this food; yaḥ retaḥ siñcati, as it procreates; tat bhūyaḥ eva bhavati, he becomes like that [its parents].

Commentary:

Here Śaṅkara explains that a person does not become the mist or cloud or paddy, etc. He merely becomes associated with these things as a person is associated with a vehicle he is riding on.

Śaṅkara also says that when a person ascends to the higher worlds, he does so in full consciousness. But when he descends, to return to this earth, he is like a person who falls from a tree and immediately becomes unconscious. His friends come and pick him up and carry him to his home without his ever being aware of it. Similarly, a person who descends from the lunar world is never aware of how he returns to the earth.