Bhagavad Gita Verse 50, Chapter 2

buddhiyukto jahaateeha ubhe sukritadushkrite |
tasmaadyogaaya yujyasva yogah karmasu kaushalam || 50 ||
 
One who is equipped with equanimity in this life discards both merit and sin. Therefore remain established in yoga; yoga results in perfect action.
 
buddhiyuktaha : with equanimity
jahaati : give up
iha : here, in this life
ubhe : both
sukritadushkrite : merit and sin
tasmaat : therefore
yogaaya : in yoga
yujyasva : established
yogah : yoga
karmasu : in action
kaushalam : perfect
 
In the last chapter, Arjuna raised several concerns to Shri Krishna while debating whether or not to fight the Kaurava army. One of the concerns was that he would incur sin if he killed his kinsmen. Having given the overview of the topic of Karmayoga, Shri Krishna wanted to now address Arjuna's concern around sin. 
 
In this shloka, Shri Krishna told Arjuna that if one follows the path of Karmayoga, i.e. performs svadharma with equanimity, one doesn't have to constantly ponder whether an action will beget merit or sin. In fact, one goes beyond the accumulation of merit or sin. Why is that the case? If we begin to detach ourselves from the results or fruits of our actions, we will also not get attached to merit and sin. Both merit and sin, like results of an action, are future-oriented expectations, and have no place in Karmayoga.
 
For instance, consider a grapevine that produces grapes. It fully carries out its svadharma, which is to produce tasty grapes. But it is upto the one who processes the grapes to make grape juice out of those grapes, or to produce alcohol that probably ends up ruining an alcoholic's family. The grapevine does not incur merit or sin, it simply performs its svadharma.
 
There is another important point in this shloka. Earlier, we came across the definition of yoga as "yoga is equanimity of mind during the performance of action". Now, Shri Krishna instructed Arjuna on another benefit of yoga. If one maintains equanimity of mind at all times, one's actions become perfect since they will be performed with total attention and dexterity, without any distractions. Therefore, there is no need worry about the result. The result will, without question, be beneficial.
 
Earlier, we had discussed trying Karmayoga using a simple exercise: washing dishes while giving complete and undivided attention to the task at hand. If you tried it, you may have noticed that it is almost impossible to focus the mind on the task. The mind, much like a child, darts either into the future or into the past. For now, let's continue to practice Karmayoga by doing simple household chores like washing dishes, but with focused attention. In the forthcoming shlokas, we will encounter more tools to bring equanimity to the mind.