This is from Bhagavad-Gita, Chapter 9, texts 1-9.
Krishna: But now I will tell you the most intimate secrets; wisdom that only my friends can understand. Learn this and you will be liberated from all misfortune. It is the monarch of all science, the supreme confidential mystery, the purest thing in the world. Applying this knowledge is very enjoyable, gives direct perception of its truths, and produces imperishable results.
Arjuna: If it is so enjoyable and tangibly beneficial, why is it so secret?
Krishna: The common man has little interest in it. They are not interested in attaining me. Instead they want some temporary paradisiac from which they soon return to the cycle of mortality.
Arjuna: Please tell me your most confidential secrets.
Krishna: I am spread throughout this entire universe, in my imperceptible form. Everything is in me, but I am not contained within anything. And so, everything is not really in me.
Arjuna: This is incomprehensible.
Krishna: That is the nature of my mystic power!
Arjuna: Can you explain it more?
Krishna: I support everyone and everything, but I am not contained within anyone or anything. I am the original entity from which all existence comes into being.
Arjuna: It is still very difficult to understand.
Krishna: I will give you an analogy to help. The atmosphere is contained within space, and space is within the atmosphere. But the atmosphere does not contain space.
Arjuna: I see! So, everything exists within you, but you are not contained within anything, even though you are within everything. I understand that now. But what happens when everything is destroyed?
Krishna: Arjuna, when a thousand ages end, everything becomes energy; my energy. When a new cycle of a thousand ages begins again, I recreate everything.
Arjuna: How do you recreate everything from energy?
Krishna: I create by again and again placing living beings into my energy, which then automatically takes different forms in conformity to their will.
Arjuna: So you are not directly responsible for the things that arise in the universe?
Krishna: Right. I am a neutral party in all this, never implicated in the causal affairs of selfish deeds of living beings.