I got the answer while reading a commentary on Isha Upanishad. We seek that based on what we understand it to be. So what we think is enlightenment or understand what enlightenment is or have heard or have been told it is will determine what it is. This is what I read : 1. We live in the a-surya loka. A world devoid of light (a capacity to see the reality as it exists) because there is no prevailing light. Even the smallest flame brightens the space around when we are in a dark room. So the final stage of enlightenment is to get to hold the flame and see all that exists with clarity.
It also answers / guides how to proceed. This is what it says.
2. We view existence when awake limited by I-ness, my-ness / not my-ness, our body, our relationships and associations of sorts and our understanding. The associations are the blocks. Then in sleep we view existence limited by the mind. It is the mind which uses stored memories, relationships and associations to generate existence which we hold true in that state. Then in deep sleep stage we are in an ocean of null-ness. We know of its existence but not what it is. The reality is beyond that state. Why? We will now see. Our consciousness is limited by our body (personal existence), in sleep consciousness is limited by our mind. We have no consciousness of what exists when we are in deep sleep. We conclude its existence by inference not knowing what it really is. Then about the fourth state - it is impenetrable, knowable like being a fish that has become one with the water, meaning it is of water, living in water, gulping and throwing out water. That is its reality. So also of the fourth state we are the whole and at the same time every minutes to part of the whole whether we be there or not like when water molecules evaporate into the atmosphere. Do they loose their waterness. No they don't. So also we are that whole in its entirety and not different from it or any part of it. We experience and infer its suchness. So be we awake, asleep, in deep sleep - literally the three worlds material, of mind, the impenetrable and the one whole remaining one with the whole as the whole is the last stage of enlightenment. That is when we see the reality by becoming one with the reality - consciousness itself like researchers build how molecules are structured using molecular models.
3. To end it all we need to understand the word Hiranyagarbha. Our life started off with a fertilised egg. So also for any and every conceivable thing or idea there is its primordial seed form. For the impenetrable wholeness is its conciousness also variously experienced one life force, one existenceness, one being, one isness. That is its Hiranyagarbha.
This one surah from the Qur-an says it all.
Allah. La ilah illa huva. Lam yalid wa lam yoolad. Wa lam yakun la hu kufwan ahad = there is nothing matching, comparable to him.
The named God - diety of Islam is the embodied version of reality.
The same is identified as Atman as partial existence and Brahman as universal existence.
The one and the all and not but it in whole and part.
Realising this is the final stage of realisation of enlightenment, of emancipation. It is ever present without beginning or end. Ever in flux and ever existing, alive, life itself, all knowing, the being, the isness, consciousness.
Om tat sat
Hence the verse
Sahna vavatu, sahanau bhunaktu, sahaveeryam karavavahai, tejasvinam dheetamastu, ma vid vishavahi, om shanti, shanti, shantihi.
*Om sahana vavatu*
ॐ सह नाववतु
Om, may God protect both teacher and student
*Saha nau bhunaktu*
सह नौ भुनक्तु
May He nourish us together
*Saha viiryam karavaavahai*
सह वीर्यं करवावहै
May we work together with great energy
*Tejasvi Navaditamastu*
तेजस्वि नावधीतमस्तु
May our studies be enlightening.
*Maa vidvissaavahai*
मा विद्विषावहै
May there be no hate among us
*Om shanti, shanti, shanti*
ॐ शान्तिः शान्तिः शान्तिः
Om peace, peace, peace
This is my copy of post on Quora of date 24 July 2023
in answer to a question "what is the last stage of Enlightenment.