Srimad Bhagavadgita, Chapter 11, Shlokas 31-34

Tell me who You are, fierce in form. Salutation be to you, O supreme God; be gracious. I desire to fully know You who are the Prima One. For I do not understand Your actions!
The Blessed Lord said I am the world-destroying Time, grown in stature and now engaged in annihilating the creatures. Even without you, all the warriors who are arrayed in the confronting armies will cease to exist!
Therefore you rise up, (and) gain fame; and defeating the enemies, enjoy a prosperous kingdom. These have been killed verily by Me even earlier; be you merely an instrument, O Savyasacin (Arjuna).
You destroy Drona and Bhisma, and Jayadratha and Karna as also the other heroic warriors who have been killed by Me. Do not be afraid. Fight! You shall coner the enemies in battle.