Supreme Truth cannot be defined in words – Bhagavad Gita Chapter II

Know that all-pervading self is eternally existent. Nobody can destroy it. But the body through which this eternal, indestructible, spirit express is perishable. So why don’t you fight? One who thinks that the Spirit kills or that the Spirit is killed is a fool.

The spirit does not kill, nor can it ever be killed. It knows neither birth nor death. It cannot come to exist or cease to exist.

It is unborn, eternal, changeless and ancient. It is not slain when the body is slain. When one knows the self to be indestructible, eternal and changeless, tell me, Arjuna, who kills whom?

Just as we discard old clothes and put on new ones, the embodies casts off its useless body taking a new one. Weapons do not injure the Self. Fire does not burn It. Water does not drench it. Wind does not dry it. Thus the self cannot be affected by anything. It, at all times, remains as ever-lasting, all pervading, stable, immovable and ancient. It cannot be perceived by the naked eye. It cannot be defined in words. It cannot be changed by time. When you know the nature of the soul, where is the scope for grief?

– Bhagavad Gita Chapter II

Source - Gita for Children by Swami Chinmayananda