Shiva Purana
उपदेशक्रमो ह्यादौ वक्तव्यश्श्रूयतामयम्॥ चातुर्व्वर्ण्यं हि लोकेस्मिन्प्रसिद्धम्मानुषे मुने ॥ २१ ॥
The order of instruction shall be mentioned at first. Please hear, O sage, indeed the four castes are well known in the world.
english translation
upadezakramo hyAdau vaktavyazzrUyatAmayam॥ cAturvvarNyaM hi lokesminprasiddhammAnuSe mune ॥ 21 ॥
hk transliteration by Sanscript