Skandapurana 5.81.13

5.81.13

yasmānme purataḥ pāpe kāṃtasya mama harṣitā..
śayyāyāṃ tvaṃ samāviṣṭā lajjāṃ tyaktvā sudūrataḥ ..
tasmādaśvamukhī nūnaṃ vikṛtā tvaṃ bhaviṣyasi .. 13 ..

“Since, casting shame far away, you have joyfully sat upon the bed / of my beloved in front of me, O sinful girl, / therefore you shall surely become deformed with the face of a horse!”