Shiva Purana
अश्वत्थामा महावीरो महादेवांशजो मुने ॥ तदापि तद्भक्तिवशः स्वप्रतापमदर्शयत् ॥ १९ ॥
O sage, although the great hero Aśvatthāman was born of a part of lord Śiva. Still due to his devotion to the Kauravas, he exhibited his full vigour.
english translation
azvatthAmA mahAvIro mahAdevAMzajo mune ॥ tadApi tadbhaktivazaH svapratApamadarzayat ॥ 19 ॥
hk transliteration by Sanscript