Bhagavad Gita Verse 24, Chapter 16

tasmaachhaastraam pramaanam te karyaakaaryavyavasthitau |
jnyaatvaa shaastravidhaanoktam karmam kartumihaarhasi || 24 ||
 
Therefore, the scripture is the authority to guide you towards what is to be not and what is not. Knowing this, you should perform actions according to scripture here.
 
tasmaat : therefore
shaastraam : scripture
pramaanam : authority
te : you
karyaakaaryavyavasthitau : guide to what is to be done and what not
jnyaatvaa : knowing this
shaastravidhaanoktam : according to scripture
karmam : actions
kartum : perform
iha : here
arhasi : should
 
Shri Krishna concludes the sixteenth chapter with this shloka. He says that ultimately it is the prompter of our actions, our motivation, that determine whether we are behaving as divine entities or as devilish ones. If the prompter of our actions is selfish desire, we are heading in the wrong direction. If the prompter is scripture, we are heading in the right direction. Therefore, when in doubt, we should refer to the guidelines in the scriptures on the performance of actions.
 
A case in point is Arjuna’s fundamental question: is it right to harm another individual? A soldier of the army defending his country and a gangster shooting at a crowd are performing the same action - killing people. But the difference is the prompter of both those actions. The soldier is prompted by duty to his country, whereas the gangster is prompted by greed. Where did the soldier’s duty come from? We could say that it came from the army’s code of conduct. We could say that it come from the constitution of his country. We could say that it came from the values cultivated by his parents.
 
In all these cases, the soldier’s sense of duty came from a set of guidelines that were founded on something that was much larger than the narrow viewpoint of one individual, that kept the bigger picture in mind. This is what Shri Krishna refers to as scripture. Using the word "here" in the shloka, he reminds Arjuna that such intelligent living is only possible in a human birth, not in any other birth. Now, we come to an interesting question? Which authority, which scripture should one follow? In this day and age, how can one practically lead an intelligent life that follows a selfless set of guidelines, that follows a scripture? This intriguing question is tackled in the next chapter.
 
om tatsatiti shreematbhagavatgitasupanishadsu brahmavidyaayaam yogashaastre shreekrishnaarjunsamvade daivaasurasampadvibhaagayogo naama shodashodhyaayaha || 14 ||