Skandapurana 5.161.5

5.161.5

brahmaghnastvaṃ yataḥ proktāstrayo varṇā dvijottamāḥ ..
brāhmaṇaḥ kṣatriyo vaiśyaḥ smṛtiśāstraprapāṭhakaiḥ .. 5 .. ..

For you are the killer of a brahmin, since the three varṇas are declared
to be twice-born, O best of brahmins—brahmin, kṣatriya, and vaiśya—by the expounders of the smṛti treatises.”