Vishnupurana 2.11.13

2.11.13

sargādau ṛṅmayo brahmā sthitau viṣṇur yajurmayaḥ
rudraḥ sāmamayo 'ntāya tasmāt tasyāśucir dhvaniḥ //

But this triple energy of Vishńu is not limited to the sun alone, for Brahmá, Purusha (Vishńu), and Rudra are also made up of the same triform essence. In creation it is Brahmá, consisting of the Rig-veda in preservation it is Vishńu, composed of the Yajur-veda; and in destruction Rudra, formed of the Sáma-veda, the utterance of which is consequently inauspicious.