Revākhaṇḍa ascribed to the Vāyupurāṇa (RKV) 166.7

166.7

navamyāṃ ca mahārāja snātvā devīmupoṣitaḥ /
pūjayet parayā bhaktyā śraddhāpūtena cetasā //

And on the ninth day, O great king, having bathed and fasted, / one should worship the Goddess with supreme devotion and a mind purified by faith;