During his life a man does not merely do things which yield pleasure; he lives also in the company of other men and other creatures. Consciously or unconsciously, intentionally or unintentionally, he causes pleasure and pain, joy and sorrow, to animals and men. All such occasions he will encounter again as he lives through the Kamaloka period; he returns to the place and moment when he was the cause of pain to another being. At that time he made someone else feel pain; now he has to suffer the same pain in his own soul.
All the torment I ever caused to other beings I now have to live through in my own soul. I enter into the person or the animal and come to know what the other being was made to suffer through me; now I have to suffer all these pains and torments myself. There is no way of avoiding it. All this is part of the process of freeing oneself — not from the working of karma, but from earthly things.
Source: Rudolf Steiner – GA 95 – At the Gates of Spiritual Science – Lecture III: Life of the Soul in Kamaloka – Stuttgart, 24rd August 1906