Revākhaṇḍa ascribed to the Vāyupurāṇa (RKV) 159.20

159.20

vātako jalahartā ca dhānyahartā ca mūṣakaḥ /
aprāptayauvanāṃ gacchan bhavet sarpa iti śrutiḥ //

A stealer of water becomes a diver-bird, and a stealer of grain becomes a mouse;
one who has intercourse with a girl who has not reached puberty becomes a serpent—such is the sacred tradition.