Which part of Islamic knowledge was also lost in ancient time?


Hazrat Adam (A) was delivered the message about Akaid i.e. believe in Allah (SWT) to all the people. But after a long interval the Prophet Nuh (A) observed nobody have believed in Allah (SWT). About 950 years counselling to the people, only about 80 people entered into Islam. After the devastating flood remaining all the people (about 80) believed in Allah (SWT). But at a certain time interval the Prophet Ibrahim (A) observed nobody existed in the world for worshiping to Allah (SWT). And he constructed the Kaaba Sharif for worshiping to Allah (SWT) only. Similarly, Prophet Hazrat Muhammad (SAW) observed that instead of worshiping to Allah (SWT) 360 idle were present in the Kaaba as Goddess.

In Indian sub-continent not only Tasauf knowledge was lost, the five times obligatory Salat prayer was also lost few hundred years ago. Five times Azan was also absent from the Mosque. At morning and evening was making Azan only for awaking about time and there were no Imam or Muazzin (who are making Azan). People were surprised by hearing Azan at day time. Hazrat Maulana Karamat Ali (Rh) mentioned in Zadut Takwa Kitab-  “When I have arranged five times Azan, most of the people asked we heard Azan at morning and evening only. It is a new rules of Salat.”

The history about loss of Tasauf from Islam can also be found elaborately in life story of Hazrat Maulana Karamat Ali written by Maulana Abdul Baten Jainpuri.  The 4th Khalifa of Islam Hazrat Ali (R) was started invitation to the people for entering into Islam. At a certain interval he observed that if one influential non-believer (Kafir) leader enter into Islam, there is an opportunity many non-believer will be followed that leader. For that reason, sometimes Hazrat Ali (R) make hello to that leader on the way. The Kafir leader also replied in the same manner. For time being, they had a good relation. At one stage Ali (R) asked him I need to discuss about some important matters with you. Where would be the suitable place for the discussion? The Kafir leader replied may be your house is the suitable place for our discussion. So they fixed a date and time schedule for the discussion. At specific time and date they sat together regarding the special discussion. At the beginning of discussion the Kafir Leader asked to Ali (R), you supposed to think one person came to your house as a guest but he don’t like to take any food, in that case there is no meaning to prepare some food for that person. Similarly. I (Leader) don’t like to hearing about Allah (SWT), Prophet (SAW), Quran and Hadith. Because I don’t believe in Allah (SWT), Rasul, Quran, Hadith and Day of Judgement. So except these issues you can talk with me and I will listen carefully.