Bhagavatapurana 10.84.19

10.84.19

brahma te hṛdayaṃ śuklaṃ tapaḥ-svādhyāya-saṃyamaiḥ /
yatropalabdhaṃ sad vyaktam avyaktaṃ ca tataḥ param //

19. The Veda is Thy absolutely pure heart: for by means of study, tapas and self-control Brahman is therein realised as the pure existence, as the effected world and as the subtle cause beyond them.