Bhagavad Gita Verse 5, Chapter 3

na hi kaschitkshanamapi jaatu tishthatyakarmakrita |
kaaryate hyaavashah karma sarvah prakritijairgunaih || 5 ||
 
For no one can stay without performing action, even for a moment. All beings, helplessly, are compelled to act by the gunaas born of prakriti.
 
na : not
hi : for
kaschit : anyone
kshanamapi : for even a moment
jaatu : in any state
tishthati : stay
akarmakrita : without performing action
kaaryate : compels to act
avashah : helplessly
karma : action
sarvah : all beings
prakritijaih : born of prakriti
gunaih : gunaas
 
Imagine a huge forest untouched by man, like we see on the National Geographic channel. If we look at it superficially, we could conclude that there is nothing going on there. But if we pay close attention, we will begin to hear the chirping of the crickets, the babble of a brook, the fluttering of wings and so on.
 
Watching all the actions going on in the forest reminds us of a simple fact. It is the tendency of nature or "prakriti" to act continuously. It never stays action-less even for a moment. Even a rock that seems action-less is undergoing geological change that is visible only after thousands or millions of years.
 
Now let us shift our attention to the human body. It too, is constructed by nature. It is composed of substances derived from the food we eat, the water we drink and the air we breathe, all products of nature. If our body is made of components born out of nature, wouldn't it also follow the tendency of nature towards continuous action?
 
Therefore, Shri Krishna informs us that all beings have no choice but to act, because all beings are made up of prakriti. He explains that prakriti is nothing but three gunaas - energies or forces that make up this entire universe. These three energies are: rajas which causes movement, tamas which causes inertia, and sattva which maintains harmony between movement and inertia. This topic is taken up in great detail in later chapters.
 
In this way, Shri Krishna addresses the question raised earlier: "Why can't I retire to the forest and cease all action?" We cannot, because the gunaas that we are made up are born out of nature, and nature never ceases to act continuously.
 
If this answer still does not satisfy us, let's try to sit still for three hours. Even if we somehow manage to physically sit still, our minds will be racing with thoughts. And even the act of thinking is an action.