Verse 1.2.1

तदेतत्सत्यं मन्त्रेषु कर्माणि कवयो यान्यपश्यंस्तानि त्रेतायां बहुधा संततानि ।
तान्याचरथ नियतं सत्यकामा एष वः पन्थाः सुकृतस्य लोके ॥ १ ॥

tadetatsatyaṃ mantreṣu karmāṇi kavayo yānyapaśyaṃstāni tretāyāṃ bahudhā saṃtatāni |
tānyācaratha niyataṃ satyakāmā eṣa vaḥ panthāḥ sukṛtasya loke || 1 ||

1. The various karma which seers found in the mantras are true and were much practised in the Treta age; practise them always with true wishes. This is your way to the attainment of the fruits of karma.

Shankara’s Commentary:

Com.—By the text the Rig Veda, the Yajur Veda, etc., all Vedas with their angas (appendages) have been stated to be apara vidya; and para vidya has been specifically stated to be that knowledge by which the akshara described in the text beginning with “That which cannot be perceived, etc,.” and ending with “Name, form and food are produced”, is known. Hereafter, the next text is begun to distinguish between the bondage of samsara and emancipation, the subjects of these two sorts of knowledge respectively. Of these, the subject of apara viyda is samsara which consists in the variety of action, its means such as doer, etc., and its results, is without beginning or end, and being misery in its nature, should be discarded by every embodied being; and in its entirety it is of an unbroken connection like the stream of a river. The subject of para vidya is emancipation which consists in the cessation of samsara, which is beginningless, endless, undecaying, immortal, deathless, fearless, pure and clear and is nothing but being centred in self and transcendant bliss without a second; first it is attempted to elucidate the subject of apara vidya; for, it is only when it is seen that it is possible to get disgusted with it; accordingly it will be said later on “Having examined the world attained by karma”; and as there can be no examination of what is not presented to the view, the text shows what it is. ‘Satyam.’ True.” What is that? Mantreshu, in the Vedas known as Rig, Yajur, etc. ‘Karmani’, Agnihotra and the rest disclosed by texts of the Vedas; ‘Kavayah,’ ‘seers like Vasishtha and ‘others’. Apasyan have seen. This is true because they are the unfailing means of accomplishing the objects of man. These enjoined by the Vedas and seen by the Rishis were done in diverse ways by the followers of karma. Tretayam, i.e., wherein there is the combination of the three Vedas of the three inodes of rites performed with the aid of a hota, adhvaryu and udgata, or it may mean that they were generally performed in the Treta age. Therefore, you should do them always; ‘Satyakamah’ ‘wishing for those fruits which they can bear.’ This is your route for the attainment of the fruits of Karma. Sukritasya, performed by you; Loka is what is found, or enjoyed; hence the fruits of Karma are denoted by the word “LoJca.” The meaning is that, to attain them, this is the route. These Karma, Agnihotra and the rest enjoined in the Vedas form the road, i.e., the means for the attainment of the necessary fruits.