For God there is no time because He is Eternal, Perpetual, Immortal.
He is forever.
For Him nothing is changing; everything is static.
He is not born of someone. All who are begotten by the process of procreation enter the world of change.
You have to find within your own self the unborn one.
This body is born, it will die. It is born by the conjunction of two bodies; it will disintegrate some day. When the bodies that gave birth to it have perished, how can something remain which is a component of the two?
The timeless has penetrated within this body; the body is no more than a piece of clothing to the timeless. That which is beyond time dwells within the time-bound.
Only when you attain the timeless being within your own self will you be able to understand Nanak's words.
You have to seek within yourself that which never changes, that which is changeless.
If you practice just sitting with your eyes closed, you will be unable to make out within yourself what age you are. You would feel yourself the same inside at the age of fifty as you felt at the age of five – as if time has not passed for the world within you. Close your eyes and you will discover that nothing has changed inside.
God means the Totality
The day you attain the unborn within you, you will know that God has no origin, no source, because God is the entirety; He is the aggregate of all things.
How can the totality be born to a particular someone?
There is nothing beyond totality for there to be a mother and father, so He is ”Never born, self-creating.”
The meaning of self-creating is that the Supreme Being exists by Himself and has no support except His own; He is self-begotten and has no origin.