SB 11.17.40

All civilized men must participate in sacrificial performances, give charity and study the Vedic literature. The best of the twice-born, namely the brāhmaṇas, are specifically empowered to lead sacrificial performances on behalf of all members of society, teach everyone Vedic knowledge and receive everyone’s charity. Without the assistance or participation of qualified brāhmaṇas, the lower classes cannot properly study the Vedic literature, perform sacrifices or give in charity, because they do not have the required intelligence to perfectly execute such functions. When kṣatriyas and vaiśyas take shelter of bona fide brāhmaṇas, they are able to properly execute their respective duties, and society functions smoothly and efficiently.