All these different social divisions are born, with their occupational duties and living conditions, from the Supreme Personality of Godhead. Thus for unconditional life and self-realization one has to worship the Supreme Lord under the direction of the spiritual master.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
एते वर्णाः स्वधर्मेण यजन्ति स्वगुरुं हरिम् । श्रद्धयाऽऽत्मविशुद्ध्यर्थं यज्जाताः सह वृत्तिभिः
ete varṇāḥ svadharmeṇa yajanti svaguruṃ harim | śraddhayā''tmaviśuddhyarthaṃ yajjātāḥ saha vṛttibhiḥ
SB 3.6.34