Mudgalapurana 2.65.53

2.65.53

ilvalaścā'pi yogīndra varayuktaprabhāvataḥ |
gatvodare kāmarūpo vātāpyāhūta eva saḥ ||

And Ilvala too, O lord of yogins, through the power of a boon, / having entered the belly and assuming any form at will, is simply summoned by Vātāpi.