This is from Bhagavad-Gita, Chapter 9, texts 11-19
Arjuna: But here you are standing in front of me with two arms and two legs. How can you be the source of everything in the universe?
Krishna: Fools think that I am limited within the shelter of a human body. You are not such a fool, Arjuna.
Arjuna: How do you know I am not?
Krishna: Because such fools take shelter of the material world. Intoxicated by it they become ungodly, wild, and mindless. They develop useless ambitions, useless endeavors, and useless understandings.
You, on the other hand, are a great soul: you take shelter of the spiritual world, and adore me without ulterior motive, because you understand that I am the inexhaustible origin of everything.
Arjuna: How are you so sure of this?
Krishna: One’s heart is obvious in one’s actions.
Arjuna: What actions of mine convince you that I am such a great soul?
Krishna: The great soul always strives with determined commitment to constantly perform kīrtana: constantly glorifying me and constantly offering me affectionate respect and worship.
Arjuna: Are there other ways to worship you?
Krishna: Most people worship me indirectly in many different ways; for example, in the effort to gain understanding, as the oneness uniting plurality, and as the personification of the universe itself.
Arjuna: Is this less perfect than the great soul who constantly strives to do your kīrtana?
Krishna: Yes, because it tends to distract people away from the essence.
Arjuna: What is the essence?
Krishna: I am.
I am the ritual. I am the sacrifice. I am the ancestor’s offering. I am the sacred herb. I am the mantra. I am the oil, the fire and the offering. I am father, mother, provider and grandfather. I am the objective of “oṁ,” which purifies the Ṛg, Sāma and Yajur Vedas. I am the goal, the husband, the lord, the witness, the home, the shelter, and the sweetheart. I am creation, destruction, and existence. I am the original seed. I am warmth. It is I who withhold and send forth the rains. I am immortality and death. I am the real and unreal.