Bhagavad Gita Verse 18, Chapter 3

naiva tasya krutenaartho naakruteneha kashchana |
na chaasya sarvabhooteshu kashchidarthavyapaashrayah || 18 ||
 
For that (realized individual), there is nothing to be gained by action or inaction here. Also, he does not have even the slightest dependency on anyone for any object.
 
na : not
eva : only
tasya : that realized individual
kruten : from action
arthaha : gained
na : not
akruten : from inaction
iha : here
kashchana: any
na : not
cha : also
asya : for him
sarvabhooteshu : with anyone
kashchit : slight/even a little
arthavya : object
apaashrayah : dependency
 
In the last shloka, Shri Krishna explained that one who has found delight solely in the eternal essence loses all sense of doership. In other words, all his actions become selfless and spontaneous, like an artist who cares only about creating paintings without any expectation (art for art's sake).
 
Shri Krishna further elaborates that point in this shloka. He says that for such a person, the concept of gain or loss does not exist, nor does the notion of dependency or support from anyone or anything.
 
To better understand this shloka, let us imagine a situation where one is at the end of a critical chapter in one's life, e.g. imagine that a person has submitted his resignation and is in the last week of his job. What will be his mindset? He will suddenly become the nicest guy in the office, and the most fun guy to hang out with. Why is that? Everyone knows that he has no agenda with anyone anymore, since it does not really matter. And he can surf the web all day long, because it does not really matter whether he works or doesn't work.
 
Another example could be a person who at age 65 has just retired. He has made a decent fortune with his savings, and can live comfortably till his last day. In addition, he is quite healthy and can still work if needed. But just like in the earlier example, it does not matter whether he performs any action or doesn't. Moreover, since he does not have any dependency on anyone, his savings make him self sufficient. Therefore, for the individual that has realized the worth of the eternal essence "treasure", any other material gain or loss does not hold any meaning.
 
Ultimately, these 2 shlokas reveal the state of a realized person, who by losing all sense of doership, renounces all action. Renouncing doership is renouncing action. The topic of renunciation is covered in detail in the forthcoming chapters.