Revākhaṇḍa ascribed to the Vāyupurāṇa (RKV) 194.14

194.14

tāṃ tasmāt tatra gatvāhaṃ varaṃ dattvā tu vāñchitam /
punas tapaḥ kariṣyāmi darśayiṣyāmi vā punaḥ /
vaiṣṇavaṃ viśvarūpaṃ yad durdaśyaṃ devadānavaiḥ //

Therefore, having gone there and granted her the desired boon, / I will perform ascetic penance again or again display / that universal form of Viṣṇu which is hard to behold by gods and demons.”