Bhagavad Gita Verse 7, Chapter 14

rajo raagaatmakam viddhi trishnaasangasamudhbhavam |
tannibandhaati kaunteya karmasangena dehinam || 7 ||
 
Know rajas to be of the nature of passion, the source of thirst and attachment. It binds the body dweller by attachment to action, O Kaunteya.
 
rajaha : rajas
raagaatmakam : nature of passion
viddhi : know
trishnaa : thirst
sanga : attachment
samudhbhavam : source
tat : it
nibandhaati : binds
kaunteya : O Kaunteya
karmasangena : attachment to action
dehinam : body dweller
 
Rajas is our state of mind when it is agitated, like a glass of water that is being stirred. Imagine that we have to attend an extremely important meeting at 5 PM. It is 4:50 PM and the taxi is stuck in a traffic jam. Our mind will be in a state of rajas. A series of thoughts will suggest that we wait in the car, while another series of thoughts will suggest that we leave the taxi and start walking. Whenever our mind is agitated by a thoughts that propel us to act, we are in a state of rajas.
 
Shri Krishna says that rajas creates trishnaa or thirst for what we do not possess, and sanga or attachment towards what we already possess. Furthermore, rajas creates a vicious cycle. It fuels our desires, creates thoughts that compel us to act so that we can acquire objects, then it creates attachment to those objects which further increases rajas. Typically, rajas dominates our mind from sunrise until sunset.
 
To understand how rajas can bind, consider the case of a multi-millionaire who has recently married his young girlfriend. The millionaire is self sufficient and does not need to work to support himself. But his wife’s brothers, relatives, friends and acquaintances slowly approach him for capital to start their business, connections to get them jobs, advice on their career and so on. Soon, the millionaire ends up working all day, every day. Even though the millionaire does not need to move a finger, he gets bound by his relationship to his wife.
 
Similarly, even though the self, the "I" does not act, rajas binds the self through attachment to action and its results. It makes us say "I am the doer" and "I am the enjoyer" whereas it is actually Prakriti that is acting and providing the results. Karma yoga helps us come out of this bondage and entrapment. It teaches us to continue to act in this world, but do it in a way that removes our identification with Prakriti. We slowly start submitting the results of our actions to Ishvara, then we slowly start letting Ishvara take over the doership of our actions as well.