Matsyapurana 171.18

171.18

gopatitvaṃ samāsādya tayorevāgamadgatim
evaṃ putrāstrayo 'pyeta uktāḥ śaṃbhormahātmanaḥ //

Then Brahmâ created Bhuva a second son from His mind who also asked Him what assistance he could render Him Brahmâ told him to follow what the two Preceptors said and by their command he went down to the earth and began to study the Vedas from them In time he attained the highest position Brahmâ again created His third son Bhûrbhûvah—the knower of Sânkhya—in the same manner, who also with the directions of Brahmâ went to the two Preceptors and obtaining knowledge, acquired the highest position like his two elder brothers —14 18