Maitri (Maitrāyaṇīya) Upaniṣad 4.3

4.3

tapasā prāpyate sattvaṃ sattvātsamprāpyate manaḥ |
manasā prāpyate tvātmā hyātmāpattyā nivartata iti ||

This is indeed the remedy for the elemental Self: Acquirement of the knowledge of the Veda, performance of one's own duty, therefore conformity on the part of each man to the order to which he happens to belong. This is indeed the rule for one's own duty, other performances are like the mere branches of a stem. Through it one obtains the Highest above, otherwise one falls downward. Thus is one's own duty declared, which is to be found in the Vedas. No one belongs truly to an order (âsrama) who transgresses his own law. And if people say, that a man does not belong to any of the orders, and that he is an ascetic, this is wrong, though, on the other hand, no one who is not an ascetic brings his sacrificial works to perfection or obtains knowledge of the Highest Self. For thus it is said:
By ascetic penance goodness is obtained, from goodness understanding is reached, from understanding the Self is obtained, and he who has obtained that, does not return.

4.3.p1

atraite ślokā bhavanti ||