Skandapurana 5.203.2

5.203.2

sāṃprataṃ śīlajāṃ brūhi naṣṭavaṃśaśca yo bhavet ..
pitāmahaṃ na jānāti na ca mātāmahīṃ nijām ..
tasya śuddhiḥ kathaṃ kāryā nāgaro'smīti yo vadet .. 2 ..

Now tell of that which arises from conduct, for one whose lineage is lost— / who does not know his paternal grandfather, nor his maternal grandmother; / how should purification be performed for him who says, 'I am a Nāgara'? // 2