Mahabharata 13.23.28

13.23.28

brāhmaṇāṃścābhimanyeta gurūṃścāpyabhipūjayet |
sarvabhūtānulomaśca mṛduśīlaḥ priyaṃvadaḥ || 28 ||

"Bhishma said,--'One should earn wealth in the first part of one's life. Then should one earn Righteousness, and then enjoy pleasure. One should not, however, attach oneself to any of these. One should regard the Brahmanas, worship one's preceptor and seniors, show compassion for all creatures, be of mild disposition and agreeable speech. To utter false-hood in a court of justice, to behave deceitfully towards the king, to act falsely towards preceptors and seniors, are regarded as equivalent (in heinousness) to Brahmanicide. One should never do an act of violence to the king's person. Nor should one ever strike a cow. Both these offences are equivalent to the sin of foeticide. One should never abandon one's (homa) fire. One should also never cast off one's study of the Vedas. One should never assail a Brahmana by words or acts. All these offences are equivalent to Brahmanicide.'