40
Śrīmad-Bhāgavatam
[Canto 7, Ch. 11]
PURPORT
The occupational duty of a  brāhmaṇa  should not be accepted by persons in lower social orders, especially  vaiśyas  and  śūdras . For example, an occupational duty of the  brāhmaṇa  is to teach Vedic knowledge, but unless there is an emergency, this professional duty should not be accepted by the  kṣatriyas ,  vaiśyas  or  śūdras . Even a  kṣatriya  cannot accept the duties of a  brāhmaṇa  unless there is an emergency, and then even if he does so he should not accept charity from anyone else. Sometimes  brāhmaṇas  protest against our Kṛṣṇa consciousness movement for creating  brāhmaṇas  from Europeans, or, in other words, from  mlecchas  and  yavanas . This movement, however, is here supported in  Śrīmad-Bhāgavatam . At the present moment, society is in a chaotic condition, and everyone has given up the cultivation of spiritual life, which is especially meant for the  brāhmaṇas . Because spiritual culture has been stopped all over the world, there is now an emergency, and therefore it is now time to train those who are considered lower and condemned, so that they may become  brāhmaṇas  and take up the work of spiritual progress. The spiritual progress of human society has been stopped, and this should be considered an emergency. Here is solid support from Nārada Muni of the movement known as Kṛṣṇa consciousness.
TEXTS 18-20
ऋतामृताभ्यां जीवेत मृतेन प्रमृतेन वा । 
  सत्यानृताभ्यामपि वा न श्ववृत्त्या कदाचन ॥१८॥ 
  ऋतमुञ्छशिलं प्रोक्तममृतं यदयाचितम् । 
  मृतं तु नित्ययाञ्जा स्यात् प्रमृतं कर्षणं स्मृतम् ॥१९॥ 
  सत्यानृतं च वाणिज्यं श्ववृत्तिर्नोचसेवनम् । 
  वर्जयेत् तां सदा विप्रो राजन्यश्च जुगुप्सिताम् । 
  सर्ववेदमयो विप्रः सर्वदेवमयो नृपः ॥२०॥
ṛtāmṛtābhyām jiveta 
  mṛtena pramṛtena vā 
  satyānṛtābhyām api vā 
  na śva-vṛttyā kadācana