Ashtavakra Gita 1.18 - Teachings on Self-Realization and Liberation

The entire visible world is formful. It is transforming too. To be so is to be unreal. For, the real is changeless. So, nothing in the formful gross world can become real. True seeker’s attention has then to be on what reigns besides the world and its objects.

Anything formless is immovable. For, a physical object moves only when an external force acts on it. The formless cannot be acted upon by another. Hence, it is immovable.

Moreover, all perceptions are inner, of and in the mind. Mind employs senses only to take its own imprints in itself. We perceive and experience anything only as mental imprints. Do the mind and its own imprints ever move from where they are? To be formless and inward, equally means not to move or vibrate.

Anything untransforming cannot be gross, formed and external. Thus the truth is both inward and permanent.
Self, Consciousness, which makes us conscious of everything and all, alone is changeless, modification-less and hence true, eternal.

This instruction alone is sufficient to make the seeker transcend birth and death, and be permanent, eternal. If the permanent is unborn and undying, where is the question of it taking any further birth?

That is why Maharshi says that the knowledge of this truth itself rules out all chance, possibility of any further birth.