It is narrated from Maaz b. Jabal that the Holy Prophet (s.a.w.s.) said: Verily Allah created me, Ali, Fatima, Hasan and Husain (a.s.) seven thousand years before the creation of the world.
Maaz asked: O Messenger of Allah (s.a.w.s.), where were you at that time? He replied – We were under the divine Throne, praising, glorifying and hallowing Allah. It was asked: What were you like? He replied: We were some bodies of light. When Allah desired to form us, He turned us into a column of light and put it in the loins of Adam (a.s.). Thereafter He continued to transfer it from loins of fathers to wombs of mothers, always keeping us away from impurity, polytheism and adultery, which was being indulged in during the time of blasphemy. In every age some groups used to be successful by putting faith in us. Some used to remain hardhearted and unfortunate as they did not believe in us. When we were brought to the loins of Abdul Muttalib that light was divided into two parts. Allah put one half of it in the loins of Abdullah and the other half in that of Abu Talib.
Thereafter my light was transferred to the womb of Amina and the other entered the womb of Fatima binte Asad. I was born from Amina and Ali (a.s.) from Fatima. Then the entire pillar returned to me and my daughter Fatima (r.a.) was born. Then that whole light was transferred to Ali (a.s.) and Hasan (a.s.) and Husain (a.s.) were born from those two parts of light. Similarly my light will continue to revolve till Judgment Day in the descendants of Husain (a.s.) in the Imams (a.s.).
Hayaat al-Quloob v 2 chap 1