Imam Sadiq (peace be upon him): Sorrow is the mark of the gnostics, because they receive an abundance of unseen inspirations, they are constantly aware of the inner reality of the world and its hidden secrets, and Allah, through His grace and favours, has veiled them. The one who is sorrowful is outwardly withdrawn, dust-covered and grieved, yet inwardly he is greatly joyful; outwardly, in society and in his dealings with people he is like the sick, but in his relationship with Allah he behaves like a close kinsman. The sorrowful is not counted as one who reflects, because the one who reflects burdens himself with effort; but sorrow is a natural matter that springs from the very nature of the human being. Sorrow arises from a person's inner self, whereas thought and reflection arise from sensible things — and there is a difference between the two. Allah the Exalted says in the story of Yaqub (peace be upon him): إِنَّما أَشْکُوا بَثِّی وَ حُزْنِی إِلَی الله وَ أَعْلَمُ مِنَ الله ما لا تَعْلَمُونَ [I only complain of my grief and sorrow to Allah, and I know from Allah what you do not know]. Beyond sorrow and grief there is something which only Allah knows and of which others have no awareness.