Kaṭha Upaniṣad 3.p45

3.p45

yathā - rathaḥ rathasthapuruṣasya grāmāntaragamanāya pradhānasādhanamevaṃ bhogā'pavargaprāpaṇāya jīvasya pradhānaṃ sādhanaṃ śarīrameva | ataḥ śarīraṃ rathatvena rūpyate | śarīraṃ rathaṃ viddhi | tatra vartamānaḥ ātmā - karmavaśyaḥ saṃsārī | tam rathinam - rathasvāminam śarīrarūparathasya svakarmabhiḥ upārjakattvāt, viddhi - jānīhi | buddhiṃ sārathiṃ viddhi - buddhiḥ atra adhyavasāyarūpā, kartavyam adhyavasyati pūrvam, tataḥ pravartate | tasmāt, buddhireva sārathiḥ | indriyarūpāśve pravartakatvasya, manodvārā buddhāveva mukhyatvāt | ato buddhiśabditam adhyavasāyaṃ sārathitvena avagaccha ityarthaḥ | manaḥ pragrahaḥ - raśanā, raśanāvabaddhasyaiva aśvasya niyantraṇam, sārathinā śakyakriyaṃ bhavati | tathā manaḥ saṃyuktānāmiva aśvatvena rūpitānāṃ nayatām indriyāṇām adhyavasāyena niyantraṇaṃ sādhyasambhavamiti1, manaḥpragrahatvena rūpitamiti, manaḥ pragrahaṃ viddhi iti bhāvaḥ ||