SB 9.9.22

parivekṣyamāṇaṁ bhagavān
 vilokyābhakṣyam añjasā
rājānam aśapat kruddho
 rakṣo hy evaṁ bhaviṣyasi
parivekṣyamāṇam — while examining the eatables; bhagavān — the most powerful; vilokya — when he saw; abhakṣyam — unfit for consumption; añjasā — very easily by his mystic power; rājānam — unto the King; aśapat — cursed; kruddhaḥ — being very angry; rakṣaḥ — a man-eater; hi — indeed; evam — in this way; bhaviṣyasi — you shall become.
While examining the food given to him, Vasiṣṭha Muni, by his mystic power, could understand that it was unfit to eat, being the flesh of a human being. He was very angry at this and immediately cursed Saudāsa to become a man-eater.