A brahmana is one who has assimilated the Vedic conclusions by practising mind and sense control. He speaks the true version of all the Vedas. As confirmed in the Bhagavad-gita (15.15): vedais ca sarvair aham eva vedyah. By studying all the Vedas, one should come to understand the transcendental position of Lord Sri Krishna. One who actually assimilated the essence of the Vedas can preach the truth. He is compassionate to conditioned souls who are suffering the threefold miseries of this conditional world due to their not being Krishna conscious. A Brahmana should take pity on the people and preach Krishna consciousness in order to elevate them. Sri Krishna Himself, the Supreme Personality of Godhead, personally descends into this universe from the spiritual kingdom to teach conditioned souls about the values of spiritual life. He tries to induce them to surrender unto Him. Similarly, the Brahmanas do the same thing. After assimilating the Vedic instructions, they assist the Supreme Lord in His endeavor to deliver conditioned souls. The Brahmanas are very dear to the Supreme Lord due to their high sattva-guna qualities, and they also engage in welfare activities for all conditioned souls in the material world.
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Fifth Canto, Chapter 05 – Text 24