Srimad-Bhagavatam: Canto 11 - Chapter 1 - Verse 11


वेद: प्रणव एवाग्रे धर्मोऽहं वृषरूपधृक् ।उपासते तपोनिष्ठा हंसं मां मुक्तकिल्बिषा: ॥ ११ ॥


vedaḥ praṇava evāgredharmo ’haṁ vṛṣa-rūpa-dhṛkupāsate tapo-niṣṭhāhaṁsaṁ māṁ mukta-kilbiṣāḥ


In Satya-yuga the undivided Veda is expressed by the syllable om, and I am the only object of mental activities. I become manifest as the four-legged bull of religion, and thus the inhabitants of Satya-yuga, fixed in austerity and free from all sins, worship Me as Lord Haṁsa.


The bull of religion is described in Śrīmad-Bhāgavatam (1.17.24): tapaḥ śaucaṁ dayā satyam iti pādāḥ kṛte kṛtāḥ. “In the age of Satya [truthfulness], your four legs were established by the four principles of austerity, cleanliness, mercy and truthfulness.” Śrī Vyāsadeva divided the one Veda into four — the Ṛg, Yajur, Sāma and Atharva Vedas — at the end of Dvāpara-yuga, but in Satya-yuga the whole of Vedic knowledge is easily understood by everyone simply by vibrating the syllable om. In this age there are no ritualistic or pious activities such as sacrifice, since everyone is sinless, austere and fully engaged in worshiping the Personality of Godhead, Lord Haṁsa, through the process of meditation.