Mudgalapurana 3.47.9

3.47.9

śrīviṣṇuruvāca |
vedā gurusvarūpāśca sarveṣāṃ nātra saṃśayaḥ |
tairyat sampāditaṃ deva munayaḥ sarva āgatāḥ ||

The blessed Viṣṇu said:
The Vedas have the nature of the Guru for all; of this there is no doubt.
Whatever is established by them, O god, all the sages have arrived [to hear].