Manusmriti
शूद्रं तु कारयेद् दास्यं क्रीतमक्रीतमेव वा । दास्यायैव हि सृष्टोऽसौ ब्राह्मणस्य स्वयम्भुवा ॥ ४१३ ॥
But a Sudra, whether bought or unbought, he may compel to do servile work; for he was created by the Self-existent (Svayambhu) to be the slave of a Brahmana.
english translation
zUdraM tu kArayed dAsyaM krItamakrItameva vA । dAsyAyaiva hi sRSTo'sau brAhmaNasya svayambhuvA ॥ 413 ॥
hk transliteration by Sanscript