A successful journey

indriyāṇi hayānāhurviṣayāmsteṣu gocarān |

ātmendriyamanoyuktaṃ bhoktetyāhurmanīṣiṇaḥ ||1.3.4||

They declare the sense organs to be the horses and the objects to be their paths.

The wise men declare that (the jīvātmā), along with the body, sense organs and the

mind, is the experiencer.

āhuḥ - they (the experts of metaphor) called indriyāṇi hayān - sense organs like eyes, ears, etc., are horses, because of the similarity of the sense organs dragging the physical body from place to place to experience sense objects, to horses dragging the chariot to experience different roads. viṣayāmsteṣu gocarān - and sense objects like forms, sound etc., are compared to the road, where horses travel on. Objects for our sense organs are form, smell, etc., not the object per se, because the form, smell, etc., are perceived by the sense organs. The sense organs are not interested in the object itself, but in the experience derived from that object. It is because our five sense organs are manifested in keeping with the five basic elements in this world.

āhurmanīṣiṇaḥ - the wise men declared that ātmendriyamanoyuktaṃ bhokteti - jīvātmā, along with the body, sense organs, and the mind, is the experiencer, because jīvātmā is the one who identifies with the body-mind-senses and their function. Not paramātmā.

After describing jīvātmā endowed with the body-mind-senses as the traveller using the metaphor of chariot, now śruti is going to talk about the kind of traveler will have a successful journey. In here, śruti only talks about śreyas (jñāna-mārga) as the direct path equipped with certain conditions for a successful journey. The general rule is that for any journey to be successful, the instrument of the journey (the vehicle) must be made journey-worthy.

yastvavijñānavān bhavati ayuktena manasā sadā |

tasyendriyāṇyavaśyāni duṣṭāśvā iva sāratheḥ ||1.3.5||

Suppose there is one who is without discrimination (and) always with an

undisciplined mind. His sense organs (will be) uncontrollable like the unruly horses

of the charioteer.

In the Bhagavad Gītā, Krsna borrows this mantra and incorporates it into verse 6.6, saying that if one has mastery over one’s body-mind-senses, then that body-mind-senses is a friend to oneself. On the other hand, if the mastery is not there, it becomes the enemy of oneself.

First, śruti gives an example of a vehicle that acts as an enemy. It is driven by a non-discriminative charioteer who chooses the wrong path, and is also unskillful in managing the disobedient horses. Similarly, when one doesn’t have a discriminative intellect, he might choose adharma over dharma, and because of the undisciplined mind, he couldn’t control the sense organs which are bound by excessive likes and dislikes.

yastvavijñānavān - one whose intellect is bereaved of discrimination between dharma and adharma, to be done and not to be done, etc., just like an unskillful charioteer who doesn’t know how to conduct the chariot. ayuktena manasā sadā - one whose mind is unfocused and indisciplined most of the time, couldn’t manage his senses which are like uncontrollable horses for the charioteer -  tasyendriyāṇyavaśyāni duṣṭāśvā iva sāratheḥ.

And there is another vehicle that acts as a friend for the traveler.

yastu vijñānavān bhavati yuktena manasā sadā |

tasyendriyāṇi vaśyāni sadaśvā iva sāratheḥ ||1.3.6||

Suppose there is one who is with discrimination (and) always with a disciplined

mind. His sense organs will be controllable like the tame horses of the charioteer.

Whereas opposed to the one earlier, if one has a discriminative intellect to choose dharma over adharma; knowing what to do in the right time; always has a discipline and focus mind; mastery over the sense organs whenever in engagement and at time of withdrawal, are possible by will, he will travel smoothly, just like riding on a chariot which has a skilful charioteer and obedient horses.

The next three mantra are talking about the results of the journey by these two kinds of charioteers.

yastvavijñānavān bhavati amanaskaḥ sadā’śuciḥ |

na sa tat padamāpnoti samsāram cādhigacchati ||1.3.7||

Suppose there is one who is without a discriminative intellect, without a

(disciplined) mind, and ever impure. He does not attain that goal. He attains

saṁsāra also.

The relationship between the means and its end is presented here. yastvavijñānavān bhavati - one who lacks of discriminative intellect, and amanaskaḥ - doesn’t have discipline of mind, sadā’śuciḥ - he is a person with an impure mind (deluded mind) most of the time, na sa tat padamāpnoti -  he will not attain the destination/goal with that kind of driver (which has been talked about earlier). He is not just failing to attain moksa, but samsāram cādhigacchati - he attains (continuing) the life of samsāra characterised by cycle of birth and death. He lost the opportunity to get out from the realm of samsāra.