Bhavad Gita III:13

In this verse, the Gita lauds one of the principles of the Vedic sacrifice. In the Brāhmaṇas, the उच्छिष्ट (ucchiṣṭa) which is the left over (food) after the sacrifice, was the preserve only of the Brahmin priests who perform the yajña. In the Gita, it is portrayed as something 'the good' consume, showing a broader base, a more inclusive stance. Today of course it has metamorphosed into our beloved 'prasad' which each and every one of us can enjoy irrespective of caste, colour, creed or gender! Enjoy the verse.

यज्ञशिष्टाशिनः सन्तो

मुच्यन्ते सर्वकिल्बिषैः

भुञ्जते  ते त्वघं पापा

ये पचन्त्यात्मकारणात्

The good who eat the remainder of the sacrifice, are released from all evils;

But the wicked, who cook only for their own sake, verily eat impurity.

Out of sandhi, and out of compound* (so to speak)  the verse looks like this:

यज्ञ+शिष्ट+आशिनः सन्तः

मुच्यन्ते सर्व+किल्बिषैः
भुञ्जते तु अघम् पापाः 
ये पचन्ति आत्म+कारणात्

यज्ञशिष्टाशिनः  = यज्ञशिष्ट  + आशिनः 

यज्ञशिष्ट  - remainder of the sacrifice, (neuter) also knows as उच्छिष्ट
 आशिनः  - [they] eating (masc., nominative, plural from √aś) 

(यज्ञशिष्टाशिनः those who eat the remainder of the sacrifice (masc., nom., plural, tatpurusha compound)

सन्तः - good existing, true (masc., nominative, plural - noun not adjective)

मुच्यन्ते सर्वकिल्बिषैः

मुच्यन्ते - they are released, liberated (3rd person, plural, passive,* present √muc, agreeing with सन्तः)  

सर्वकिल्बिषैः sins, evils, wrong (neutral instrumental plural. Karmadharya* compound that translates in to English as 'from all evils'. In Hindi it would be किल्बिष से)

भुञ्जते - they eat, enjoy (3rd person, plural, present, ĀP* √bhuj)
ते - they
त्वघं = तु + अघम् (sandhi between u and a = va. We'll be covering this soon) 
तु - indeed, verily (avyaya) 
अघम् - impurity, pain, suffering (neut., accusative, singular)
पापा - the wicked, the evil [ones] (masc., nom., plural) It is actually पापाः  but the visarga is dropped by the rules of sandhi before the य of the next word

ये पचन्त्यात्मकारणात्

ये - [those] who (masc., nom., plural) Hindi - वह जो
पचन्त्यात्मकारणात् = पचन्ति + आत्म + कारणात्

पचन्ति - [they] cook/digest (3rd person, nom., plural, present √pac)

आत्म - (neut.) self, own [as it appears in a compound]

कारणात् - lit. from the cause; for the sake of [the self] Hindi: अपने कारण से

* For readers who are visiting for the first time, the underlined words/concepts are to be covered in the course that begins October 1.