Sound and Light

Two things namely, Sound and Light serve as guides in the World. These are also called Kalam, Sound, and Noor, Light. These are the two Paths by following which one progresses on the path of spirituality. Both are fruitful. They are related to the practice of listening to the Inner Sound and seeing the Inner Light. Each has its own place. There is Light inside us and it contains Sound within it. 

True devotion springs from contact with this Light and Sound:

When the mind was attuned to the Shabd; it became detached and dispassionate, there appeared Light within and from It emanated the Heavenly Sound which made me a devotee of the True Lord.

Sorath M1, 634-12

The Sound and the Light, in reality, are one. Vibrations up to a certain extent produce sound; but if their frequency is increased several-fold, they change into light. This Sound is the real and basic life-force which sustains the entire universe. This is the Light that lights our dark homes or bodies. It is, however, imperceptible to the physical eyes.

That thing is beyond the domain of perception.

Gauri M5, 205-3

Without the Sound there is darkness inside. One perceives not the Reality. One is not rid of coming and going.

Majh M3, 124-13

It lights not only us, but the whole world. The world is dark without the Shabd. The entire world is lighted by it.

 Sarang Var M4, 1250-4

This Light is within all of us. Christ also mentions that this Light lights all. It does so without any distinction, be one a Hindu, a Muslim or a Christian. In Him was life, and the life was the Light of man. And the Light shineth in darkness—that was the True Light, which lighteth every man that cometh into the world. 

St. Augustine has also described the appearance of this light within him thus:

I entered even into my inward self, Thou being my guide, And able I was; for Thou wert become my helper. And I entered and beheld with the eye of my soul (such as it was), above the same eye of my soul above my mind, the light unchangeable. Not this ordinary light which all flesh may look upon, nor as it were a greater of the same kind, as though the brightness of this should be manifold brighter, and with its greatness take up all space. Not such was the light, but other yea, far other from all these. He that knows the Truth knows what that light is, and he that knows it, knows Eternity.

St. Augustine

Kabir Sahib says that without the Shabd the soul is blind and does not find the way, so it wanders hither and thither.

Blind is the soul without the Shabd. Oh! where can it go? It finds not the door of the Shabd. So wanders to and fro. Zoroaster also mentions the Light and even now Parsees worship the outside fire. All the great souls whether of the East or the West, who went inside and had access to the inner regions, have mentioned the Sound and the Light. The soul is imprisoned in the cage of the mind and the body. Both Light and Sound are within us. The Sound and Light are related to the two faculties of the soul namely Surat, hearing, and Nirat, seeing. 

Surat hears and Nirat sees. In ascending upward through the spiritual regions, Nirat leads and Surat follows.