Arjuna, is this hour of battle the time for scruples and fancies ? Are they worthy of you, who seek enlightenment?

Arjuna, is this hour of battle the time for scruples and fancies ? Are they worthy of you, who seek enlightenment? ...There never was a time when I did not exist, nor you, nor of any of these kings . Nor is there any future in which we shall cease to be.

What is the context of this text . In what tradition and sacred writing would you find it ? Who is speaking and ultimately what does he unveil about himself and reality?