Srimad Bhagavatam Canto 06, Chapter 07, Text 36

SB 6.7.36

akiñcananam hi dhanam siloñchanam
 teneha nirvartita-sadhu-satkriyah
katham vigarhyam nu karomy adhisvarah
 paurodhasam hrsyati yena durmatih
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
O exalted governors of various planets, the true brahmana, who has no material possessions, maintains himself by the profession of accepting siloñchana. In other words, he picks up grains left in the field and on the ground in the wholesale marketplace. By this means, householder brahmanas who actually abide by the principles of austerity and penance maintain themselves and their families and perform all necessary pious activities. A brahmana who desires to achieve happiness by gaining wealth through professional priesthood must certainly have a very low mind. How shall I accept such priesthood?
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
A first-class brahmana does not accept any rewards from his disciples or yajamanas. Practicing austerities and penances, he instead goes to the agricultural field and collects food grains left by the agriculturalists to be collected by brahmanas. Similarly, such brahmanas go to marketplaces where grains are purchased and sold wholesale, and there they collect grains left by the merchants. In this way, such exalted brahmanas maintain their bodies and families. Such priests never demand anything from their disciples to live in opulence, imitating ksatriyas or vaisyas. In other words, a pure brahmana voluntarily accepts a life of poverty and lives in complete dependence on the mercy of the Lord. Not very many years ago, a brahmana in Krsnanagara, near Navadvipa, was offered some help from the local Zamindar, Raja Krsnacandra. The brahmana refused to accept the help. He said that since he was very happy in his householder life, taking rice given by his disciples and cooking vegetables of tamarind leaves, there was no question of taking help from the Zamindar. The conclusion is that although a brahmana may receive much opulence from his disciples, he should not utilize the rewards of his priesthood for his personal benefit; he must use them for the service of the Supreme Personality of Godhead.
Srimad Bhagavatam Canto 06, Chapter 07, Text 35
Srimad Bhagavatam Canto 06, Chapter 07, Text 37