इन्द्रियाणि हयानाहुर्विषयाँ स्तेषु गोचरान् ।
आत्मेन्द्रियमनोयुक्तं भोक्तेत्याहुर्मनीषिणः ॥ ४ ॥

indriyāṇi hayānāhurviṣayām̐ steṣu gocarān ।
ātmendriyamanoyuktaṃ bhoktetyāhurmanīṣiṇaḥ ॥ 4 ॥

4. The senses, they say, are the horses; the objects which they perceive, the way; the atman, the senses and the mind combined, the intelligent call the enjoyer.

Shankara’s Commentary:

Those who are versed in the construction of chariots call the senses, such as the eye and the rest, horses, from the similitude of their drawing the body. Know the objects (such as form, etc.), of these senses, regarded as horses, to be the roads. The intelligent call the atman combined with the body, the senses and the mind, the enjoyer, i.e., one in Samsara; for, the pure atman cannot be the enjoyer. Its enjoyment is only the product of its conditions such as intelligence, etc.; accordingly also, other srutis declare that the pure atman is certainly not the enjoyer. ‘It seems to think and to move’; only if this is so, in working out the analogy of the chariot to be described, it will be appropriate to understand. ‘The Vishnu Pada’ as the pure atman but not otherwise; for, there can be no going beyond Samsara in the case of the pure atman.