Hadhrat Mawlana Muhammad Manzur Nu’mani, may Allah have mercy on him, writes:
Certainly. Just as in other branches—that is to say, both in aqa’id (beliefs) and in the practices of din— there have, in some circles of the ummah, been both minor and major aberrations. So also the branch of suluk and tasawwuf has not remained safe from error. However, just as Allah Almighty has created godly Ulama and mujtahidin to correct errors in aqa’id and practices, he has also continued to create muhaqqiqin (examiners) among the Sufis to correct errors and deviations in the branch of suluk and tasawwuf.
Particularly in the last three to four centuries the work of reform and revival of tasawwuf that has taken place in India is a first-rate example of the separation of milk from water. Here we have thick volumes of the letters of Imam-e-Rabbani Mujaddid Alf-e-Thani and his son and successor Khwaja Muhammad Mas’sum; the writings and letters of Shah Waliyullah Dehlawi and Qadi Thana’ullah Panipati; and the collected sayings and advice of Sayyid Ahmad Shahid put together by Shah Isma’il Shahid under the name “Sirat al-Mustaqim.”
May Allah shower his mercy on them all.
Thereafter, in this century, we have the booklets and letters of Mawlana Rashid Ahmad Gangohi (rahmatullahi ‘alaihi), and most recently of all, a whole library of writings on this subject by Hakim al-Ummah, Mawlana Ashraf ‘Ali Thanwi (rahmatullahi ‘alaihi).
These efforts have made tasawwuf clearly visible, and effectively cleared away all the deception and malicious propaganda (against tasawwuf), that if anyone now goes astray on this path, he really has no one to blame except himself.
So, just as it is not right of anyone on the basis of the errors of some parties in aqa’id or practice, to simply get irritated and then cease to pay any attention to aqidah and practice, it is not the right of any person—on account of the errors of some parties in the field of tasawwuf—to cease paying attention to this branch of din, without which a person’s Islam will remain incomplete, and without which he will not find the sweetness of faith.
Din And Shari’at, Zam Zam Publishers, Pages 120-121 [English translation by ‘Abd ur Rahman O’Beirne (with minor changes by the editor)]