Manava Dharmashastra 12.93

12.93

etad dhi janmasāphalyaṃ brāhmaṇasya viśeṣataḥ
prāpyaitat kṛtakṛtyo hi dvijo bhavati nānyathā //

For that secures the attainment of the object of existence, especially in the case of a Brahmana, because by attaining that, not otherwise, a twice-born man has gained all his ends.