Shiva Purana

siva.sh/siva-purana/uma-samhita/21/15

तेनाग्निमन्त्रपूतात्मा क्षत्त्रियो ब्राह्मणो भवेत् ।। विधितो ब्राह्मणो भूत्वा याजकस्तु प्रजायते ।। १५ ।।

sanskrit

By this a kshatriya whose soul is purified by the mantra of fire becomes a brahmin A priest is born a brahmin according to the prescribed rituals.

english translation

tenAgnimantrapUtAtmA kSattriyo brAhmaNo bhavet || vidhito brAhmaNo bhUtvA yAjakastu prajAyate || 15 ||

hk transliteration by Sanscript