The ब्राह्मण knows and sees the व्याध doing कर्म of a butcher. He naturally therefore asks the व्याध that being such a knowledgeable person, how can the व्याध perform acts of हिंसा. Can people aligned to the वेद perform such कर्म? This is an age-old question that never ends. Can one ever call oneself a pure vegetarian? व्याध response is an eternal truth and worth listening to. 

मार्कण्डेय उवाच

स तु विप्रमथोवाच धर्मव्याधो युधिष्ठिर | यदहं ह्याचरे कर्म घोरमेतदसंशयम् ||

Said मार्कण्डेय – O युधिष्ठिर! The धर्म-aligned व्याध said to that ब्राह्मण “The acts that I perform are no doubt cruel”. 

विधिस्तु बलवान्ब्रह्मन्दुस्तरं हि पुराकृतम् | पुराकृतस्य पापस्य कर्मदोषो भवत्ययम् ||

O ब्राह्मण! विधि (destiny) is all powerful; it is difficult to overcome the consequences of our past कर्म. Outcome of पाप done in the past life comes in the form of कर्म that one experience now.

दोषस्यैतस्य वै ब्रह्मन्विघाते यत्नवानहम् | विधिना विहिते पूर्वं निमित्तं घातको भवेत् ||

O ब्राह्मण! I always make efforts to eradicate the impact of दोष. विधि has already killed on when it is killed by the other, the executioner is but an instrument (as निमित्त). 

निमित्तभूता हि वयं कर्मणोऽस्य द्विजोत्तम | येषां हतानां मांसानि विक्रीणामो वयं द्विज ||

तेषामपि भवेद्धर्म उपभोगेन भक्षणात् | देवतातिथिभृत्यानां पितॄणां प्रतिपूजनात् ||

O द्विजोत्तम! We are but such agents in consequence of our कर्म. Those animals that are killed and those which are sold also acquire कर्म, for the देवता, guests and servants are entertained (by eating the meat) and ancestors are gratified by his food. 

ओषध्यो वीरुधश्चापि पशवो मृगपक्षिणः | अन्नाद्यभूता लोकस्य इत्यपि श्रूयते श्रुतिः ||

श्रुति (viz the वेद) states that herbs, vegetables, deer, birds and the wild animals are ordained food for all creatures. 

आत्ममांसप्रदानेन शिबिरौशीनरो नृपः | स्वर्गं सुदुर्लभं प्राप्तः क्षमावान्द्विजसत्तम ||

O ब्राह्मण! The son of Ushinara, Shibi, one having great patience, obtained स्वर्ग which is very difficult to obtain, by giving away his own flesh. 

स्वधर्म इति कृत्वा तु न त्यजामि द्विजोत्तम | पुराकृतमिति ज्ञात्वा जीवाम्येतेन कर्मणा ||

O द्विज (one learned in the वेद)! Knowing this to be by स्वधर्म, I do not give it up. Knowing this to be the result of my own कर्म, I earn my livelihood by doing this. 

स्वकर्म त्यजतो ब्रह्मन्नधर्म इह दृश्यते | स्वकर्मनिरतो यस्तु स धर्म इति निश्चयः ||

O ब्राह्मण! To abandon one’s own स्वकर्म is considered to be अधर्म. To stick to one’s own स्वकर्म is certainly an act of धर्म. 

पूर्वं हि विहितं कर्म देहिनं न विमुञ्चति | धात्रा विधिरयं दृष्टो बहुधा कर्मनिर्णये ||

The कर्म done before (in one’s previous lives) never leave any creature. In determining the effects of various कर्म, the Creator makes sure of this. 

द्रष्टव्यं तु भवेत्प्राज्ञ क्रूरे कर्मणि वर्तता | कथं कर्म शुभं कुर्यां कथं मुच्ये पराभवात् ||

A man under the effects of cruel कर्म must always introspect “What beneficial कर्म must be done and what कर्म must I do now”? 

कर्मणस्तस्य घोरस्य बहुधा निर्णयो भवेत् | दाने च सत्यवाक्ये च गुरुशुश्रूषणे तथा ||

द्विजातिपूजने चाहं धर्मे च निरतः सदा | अतिवादातिमानाभ्यां निवृत्तोऽस्मि द्विजोत्तम ||

There are various ways in which the cruel कर्म can be eliminated, such as by making दान, adhering to सत्य, serving Guru (who walk the path of वेद) and following द्विज (those who adhere to the वेद), by becoming devoted to धर्म, free from pride and idle talk. O द्विजोत्तम! I do these things. 

कृषिं साध्विति मन्यन्ते तत्र हिंसा परा स्मृता | कर्षन्तो लाङ्गलैः पुंसो घ्नन्ति भूमिशयान्बहून् | जीवानन्यांश्च बहुशस्तत्र किं प्रतिभाति ते ||

Agriculture is considered to be a praise-worthy occupation, but it is well-known that even in it, great harm is done to animal life. In the ploughing of the ground, various creatures and animal lives are destroyed. What is your opinion on this matter? 

धान्यबीजानि यान्याहुर्व्रीह्यादीनि द्विजोत्तम | सर्वाण्येतानि जीवानि तत्र किं प्रतिभाति ते ||

O द्विजोत्तम! Rice and seeds of rice are all living organisms, what is your opinion on this matter?

अध्याक्रम्य पशूंश्चापि घ्नन्ति वै भक्षयन्ति च | वृक्षानथौषधीश्चैव छिन्दन्ति पुरुषा द्विज || जीवा हि बहवो ब्रह्मन्वृक्षेषु च फलेषु च | उदके बहवश्चापि तत्र किं प्रतिभाति ते || 

O ब्राह्मण! Men hunt wild animals and kill them to eat their meat; they also cut up trees and plants. O ब्राह्मण! There are innumerable living organisms in trees and fruits and also in water, do you not think so? 

सर्वं व्याप्तमिदं ब्रह्मन्प्राणिभिः प्राणिजीवनैः | मत्स्या ग्रसन्ते मत्स्यांश्च तत्र किं प्रतिभाति ते || सत्त्वैः सत्त्वानि जीवन्ति बहुधा द्विजसत्तम | प्राणिनोऽन्योन्यभक्षाश्च तत्र किं प्रतिभाति ते || 

O ब्राह्मण! The whole universe is full of animals and animal organisms. Do you not see that fish preys upon fish and various other species of animals prey upon various other animals and there are also some who prey upon one another. 

चङ्क्रम्यमाणा जीवांश्च धरणीसंश्रितान्बहून् | पद्भ्यां घ्नन्ति नरा विप्र तत्र किं प्रतिभाति ते || 

O ब्राह्मण! A man kills innumerable animals that live on the ground by trampling upon their feet. What do you have to say to this?

उपविष्टाः शयानाश्च घ्नन्ति जीवाननेकशः | ज्ञानविज्ञानवन्तश्च तत्र किं प्रतिभाति ते || 

Even the wise and learned men kill many animals in various ways while sleeping or resting. What do you have to say to this? 

जीवैर्ग्रस्तमिदं सर्वमाकाशं पृथिवी तथा | अविज्ञानाच्च हिंसन्ति तत्र किं प्रतिभाति ते || 

The Earth and the Sky are full of animal organisms which are unconsciously killed by men from ignorance, what do you have to say to this?

अहिंसेति यदुक्तं हि पुरुषैर्विस्मितैः पुरा | के न हिंसन्ति जीवान्वै लोकेऽस्मिन्द्विजसत्तम | बहु संचिन्त्य इह वै नास्ति कश्चिदहिंसकः ||

O द्विजसत्तम! Who is there on Earth who does not do harm to any creature? After full consideration, this is the conclusion (that I have come to) that there is none who has not killed an animal. 

अहिंसायां तु निरता यतयो द्विजसत्तम | कुर्वन्त्येव हि हिंसां ते यत्नादल्पतरा भवेत् ||

O द्विजसत्तम! Even the Rishis whose vows are not to destroy living organisms (do destroy animals). Only on account of their great care, they commit less killing (of animals). 

आलक्ष्याश्चैव पुरुषाः कुले जाता महागुणाः | महाघोराणि कर्माणि कृत्वा लज्जन्ति वै न च ||

Men of noble birth and great accomplishment perpetrate wicked कर्म in defiance of all and they are not ashamed of it. 

सुहृदः सुहृदोऽन्यांश्च दुर्हृदश्चापि दुर्हृदः | सम्यक्प्रवृत्तान्पुरुषान्न सम्यगनुपश्यतः ||

Good men acting in an exemplary manner are not praised by other good men nor bad men acting in a contrary manner are praised by other bad men. 

समृद्धैश्च न नन्दन्ति बान्धवा बान्धवैरपि | गुरूंश्चैव विनिन्दन्ति मूढाः पण्डितमानिनः ||

Friends are not agreeable to friends, however accomplished they might be. Foolish even find fault with the धर्म of their own गुरू. 

बहु लोके विपर्यस्तं दृश्यते द्विजसत्तम | धर्मयुक्तमधर्मं च तत्र किं प्रतिभाति ते ||

Such reversal of natural order, O ब्राह्मण, are always seen (in this world). What is your opinion about धर्म or otherwise of this state of things? 

वक्तुं बहुविधं शक्यं धर्माधर्मेषु कर्मसु | स्वकर्मनिरतो यो हि स यशः प्राप्नुयान्महत् ||

There can be said many things about whether our कर्म constitute धर्म or अधर्म. But the one you sticks to स्वकर्म acquires great fame. 

Conclusion

What does one conclude from this long narrative? There are two conclusions one may make given that all of us are condemned to perform acts of हिंसा against all living organisms, whether knowingly or unknowingly.

1. Live a life of धर्म (align to सत्य , do दान, etc). Such कर्म will lessen the impact of acts of हिंसा that all of us indulge in. This is non-negotiable.
2. If you perform स्वकर्म, you are good. What is स्वकर्म is a detailed topic and maybe will be taken up later in the text anyway. For now, let us understand स्वकर्म as an action that we perform in line with our स्वधर्म which in turn is aligned to our स्वभाव. If one is born in a vegetarian family, do not go out of the way to eat non-vegetarian food for taste/ desire. If one is born in a non-vegetarian family, stick to such food on certain days only (to minimize the impact of हिंसा) but always live a life of धर्म (as given under a above since that aspect is non-negotiable). 

Source:

Translation of Mahabharata by MN Dutt

Sanskrit Shloka from https://bombay.indology.info/mahabharata/text/UD/MBh03.txt