Shiva Purana
क्षत्रियः पंचलक्षेण क्षत्त्रत्वमपनेष्यति । पुनश्च पंचलक्षेण क्षत्त्रियो ब्राह्मणो भवेत् १२४ ।
A Kṣatriya must repeat the mantra five hundred thousand times to remove Kṣatratva. A further repetition of five hundred thousand times enables him to become a brahmin.
english translation
kSatriyaH paMcalakSeNa kSattratvamapaneSyati । punazca paMcalakSeNa kSattriyo brAhmaNo bhavet 124 ।
hk transliteration by Sanscript