Srimad BhagavadGita

Kṛṣṇa says to Arjuna, "In the performance of actions, a person endowed with this buddhi gets rid of both good and bad results. Arjuna, you should therefore strive to abide in this buddhi. Presence of this buddhi in the performance of karmas is a great skill on par with a skill achieved due to extraordinary capabilities."

iha (While performing karmas)

buddhiyuktaḥ A person with this buddhi (intelligence) described earlier.

sukṛta duṣkṛte ubhe jahāti gets rid of both puṇyas and pāpas. 

  iha jahāti (While performing karmas he gets rid of...) When 'iha' and 'jahāti' are grouped together, it is

understood that this person gets rid of the results of his good or bad deeds in the execution phase itself, i.e in

the 'performance of karmas abiding in buddhi yoga' phase itself. Just as it is told in ihaiva tairjitaḥ sargaḥ

B.G 5.19 (They will win over saṃsāra in the practice phase itself), the certainty conveyed by 'iha jahāti'

confirms that both puṇyas and pāpas will be destroyed for such a person here itself. 

  sukṛta duṣkṛte jahāti Sukṛti or Puṇya is Paramātma's affection on a person on account of the

countless good karmas he has been performing since beginning less time for the attainment of his trivial

objectives. Duṣkṛti or pāpam is Paramātma's anger on a person on account of the countless bad karmas

he has been performing since beginning less time. The statements puṇyāpuṇyā vīśvaraprītikopau and

yattvatpriyam tadiha puṇyam apuṇyamanyat (Bhagawān's affection and anger are termed as puṇyam

and pāpam respectively) also convey the same. A practitioner of karma yoga sequentially moves to jñāna

yoga and then bhakti yoga. Due to this progression, Paramātama's affection and anger are removed and he

attains mokṣa. 

  Q: Desiring that Paramātama's anger must be removed can be understood but how can it be desired that

HIS affection too must be removed?

  A: The affection that is removed is the affection caused due to the execution of means like jyotiṣṭomā       

, etc, for attaining higher material rewards like heaven, etc. The exquisite affection caused due to the practice

of karma yoga and such other means for the attainment of mokṣa are not removed. The earlier affection leads

to attainment of heaven, etc, thus becoming a reason for the person to remain bound to this saṃsāra.

Therefore, just as Paramātma's anger caused due to one's pāpa karmas is a hindrance to his attainment of

mokṣa, even Paramātma's affection is a hindrance. From the statements of authoritative texts too like ete vai

nirayā stāt sthānasya paramātmanaḥ Mahābhārata Mokṣa parva 198.11 (When compared to Paramātma's

abode all these are like hell) and svargōpi yaściṃtane vighno yatra niveśitātmamanaso

brāhmopilokolpakaḥ Viṣṇu Purāṇa 6.8.56 (That Paramātma in whose comparison even heaven is a hurdle

and Caturmukha Brahma's loka too is insignificant), it is clear that these are hurdles to mokṣa and

equivalent to hell. It is the opinion of learned men that just as there is no difference in being bound by gold

shackles or iron shackles, both puṇyas and pāpas bind a jīva to this saṃsāra equally.

buddhiyuktaḥ jahāti plavāhyete adrudhā yajñarūpāḥ Munḍaka Up 1.2.7 (These yajñas are karmas which are like unstable boats) and na hyadruvaiḥ prāpyate hi druvaṃ tat Kaṭha Up 2.10 (unstable karmas cannot deliver a stable outcome) As declared by these authoritative statements, executing just the karmas cannot make one free of his puṇyas and pāpas. They can be removed only by the performance of karmas enjoined with the necessary buddhi. 

tasmāt (Therefore) In this way, since buddhi yoga causes release from both puṇyas and pāpas. 

yogāya yujyasva (Strive to acquire this buddhi yoga described earlier) 

yogaḥ karmasu kauśalam

karmasu (in the performance of karmas i.e in actions)

yogaḥ (abiding in this buddhi described earlier, i.e buddhi yoga)

kauśalam (is an expert skill acquired as a result of extraordinary capabilities)

In this statement, it is said that this buddhi (yogaḥ) is a great skill (kausalam) in performing actions. Both the words 'yogaḥ' and 'kauśalam' are nouns and 'karmasu' is the sabda saptami vibhakti, bahu vachanam form of the sabda 'karma' meaning 'in actions'. 

Q: Kauśalam and yogaḥ are both nouns. How can a noun (yogaḥ) be achieved through another noun (kauśalam), rather than a verb/action)?

A: Bhagawad Rāmānujā clarifies this beautifully. He quotes the meaning of kauśalam as 'ati sāmarthya sādhyaḥ iti arthaḥ' (The skill which is achieved through extraordinary capabilities). kārye kāraṇa sabda upacaritam, since it is a known practice in the śāstras to refer to the result with the same word used to refer to its cause, the word 'kauśalam' originally referring to 'capabilities' refers to the skill developed as a result of these extraordinary capabilities. nāyam ātmā balahīnena labhyaḥ Muṇḍaka Up. 3.2.4 (This soul is not attained by the weak). This statement of the upaniṣads too confirms that 'This yoga is achieved through great skill 'ati sāmarthya sādhyaḥ'.

In this way, by cultivating the said buddhi, a mumukṣu practising karma yoga can get rid of his puṇyas and pāpas.