Upadesa Sahasri is a popular work of Adi Shankaracharya
I am different from the body. The body is born, dies, is eaten by birds, turns into earth, is destroyed by weapons, fire and so forth, and suffers from disease and so on.
I have entered this body as a bird enters a nest by force of the merit and demerit accumulated by myself. Again and again by force of the merit and demerit, when this body perishes, I shall enter another body as a bird enters another next when its previous one has been destroyed. Thus I am in beginningless transmigratory existence.
I have been abandoning old bodies which have been obtained one after another in the spheres of gods, animals, men and hells by force of my own karman and I have been getting other new bodies over and over again.
I am forced by my own karman to rotate in the incessant cycle of birth and death as in a water-wheel. I have obtained this body in the course of time.