In future, human beings, the older they get, will need to take in spiritual impulses if they want to be able to grow younger and younger and really develop their inner life. If they do so, they may have grey hair and wrinkles and all kinds of infirmities, but they will get younger and younger, for their souls are taking in impulses which they will take with them through the gate of death. People who relate only to the body cannot grow younger, for their souls will share in everything the body experiences. Of course, it will not be possible to change the habit of going grey, but it is possible for a grey head to gain a young soul from the wellsprings of spiritual life.
Source: Rudolf Steiner – GA 177 – Fall of the Spirits of Darkness: Lecture 12: The Spirits of Light and the Spirits of Darkness – Dornach, 26 October 1917
Translated by Anna R. Meuss