Manusmriti

siva.sh/manusmriti/10/121

शूद्रस्तु वृत्तिमाकाङ्क्षन् क्षत्रमाराधयेद् यदि । धनिनं वाऽप्युपाराध्य वैश्यं शूद्रो जिजीविषेत् ॥ १२१ ॥

sanskrit

If a Sudra, (unable to subsist by serving Brahmanas,) seeks a livelihood, he may serve Kshatriyas, or he may also seek to maintain himself by attending on a wealthy Vaisya.

english translation

zUdrastu vRttimAkAGkSan kSatramArAdhayed yadi | dhaninaM vA'pyupArAdhya vaizyaM zUdro jijIviSet || 121 ||

hk transliteration by Sanscript