In the Shurangama Sutra, King Prasenajit is getting on in years. So, in order to reveal the Eternal Essence of Consciousness to the King – the Buddha firstly asks him how he is now, compared to when he was younger.
The King replies that he was vibrant and full of life back then, but now he is withered and wrinkled – even his spirit is dull. These changes at first seemed to be happening each decade, but no, more year by year, day by day, even moment to moment. So he realizes that his body will keep changing until it dies one day:
The Buddha told the great king, “By watching the ceaseless changes of these transformations, you awaken and know of your extinction, but do you also know that at the time of extinction there is something in your body which does not become extinct?”
King Prasenajit put his palms together and exclaimed, “I really do not know.”
The Buddha said, “I will now show you the nature which is not produced and not extinguished.
“Great king, how old were you when you saw the waters of the Ganges?”
The king said, “When I was three years old my compassionate mother led me to visit the Goddess Jiva. We passed a river, and at the time I knew it was the waters of the Ganges.”
The Buddha said, “Great king, you have said that when you were twenty you had deteriorated from when you were ten. Day by day, month by month, year by year until you have reached sixty, in thought after thought there has been change. Yet when you saw the Ganges River at the age of three, how was it different from when you were thirteen?”
The king said, “It was no different from when I was three, and even now when I am sixty-two it is still no different.”
The Buddha said, “Now you are mournful that your hair is white and your face is wrinkled. In the same way that your face is definitely more wrinkled than it was in your youth, has the seeing with which you look at the Ganges aged, so that it is old now but was young when you looked at the river as a child in the past?”
The king said, “No, World Honored One.”
The Buddha said, “Great king, your face is in wrinkles, but the essential nature of your seeing has not yet wrinkled. What wrinkles is subject to change. What does not wrinkle does not change.
“What changes will become extinct, but what does not change is fundamentally free of production and extinction. How can it be subject to your birth and death? Furthermore, why bring up what Maskari Goshaliputra and the others say: that after the death of this body there is total extinction?”
The king heard these words, believed them, and realized that when the life of this body is finished, there will be rebirth. He and the entire great assembly were greatly delighted at having obtained what they had never had before.