One of the most dependable and scholarly collection of biographies of Indian Sufis is the 'Akhbarul-Akhyar fi Asrarul-Abrar'. The author, Shaikh Abdul Haqq bin Saifuddin al-Turk al-Dihlawi (may Allah be pleased with him), was born in January-February 1551 and died 1642-43. His entire life was spent in an unremitting pursuit of knowledge, and his studies took place both in India and Hejaz. Being trained as a scholar of Hadis, he was famous as a muhaddis. His close male ancestors were and relatives were also scholars and mystics. His library was extensive and included all the malfuzat and Sufi works written in India, as well as a large number of books written outside India. Shaikh Abdul Haqq (may Allah be pleased with him) was a masterly critic of Hadis and was therefore well equipped to investigate authenticity and historical value of religious traditions and his skill can be clearly seen in his 'Akhbarul-Akhyar fi Asrarul-Abrar' which incorporated 225 biographies of Indian Sufis. The book began with a note on Shaikh Sayyiduna Abdul Qadir Jilani (may Allah be well pleased with him) and ended with an account of the authors own ancestry and some details of his life.
According to the author S.A.A Rizvi [A History of Sufism in India, Volumes 1 and 2]:
[his] writings on Sufism are generally an attempt to reconcile Shariah with the Tariqa; nevertheless they also assert the superiority of Shaikh Sayyiduna Abdul Qadir Jilani (may Allah be well pleased with him) and the Wahdat al-Wujud. His celebrated Akhbarul-Akhyar, relating to Indian Sufis emphasizes the belief that Shaikh Abdul Qadir Jilani (may Allah be well pleased with him) was superior to all his predecessors and that his precedence over the future generations of Saints of God was also guaranteed. To Shaikh Abdul Haqq, the Ghaus-ul-Azamís claim, "My foot is on the neck of every Saint of God" was a well-considered statement.
Using as model of the Tabaqat literature of the biographies of narrators and transmitters of the Ahadith [traditions of the beloved Prophet Muhammad (Allah bless him and give him peace)] and of the Sufi Tabaqat literature, Shaikh Abdul Haqq (may Allah be well pleased with him) classified the biographies into three sections (tabaqas) which covered the following Sufis:
1. Kwaja Muinuddin Sijzi, his contemporaries and disciples
2. Shaikh Farididdin Ganj-I Shakar and his followers and disciples
3. Shaikh Nasiruddin Mahmud Chiragh-i Dihli and Sufis from that time to that of his [may Allah be pleased with
Such a classification helped Shaikh Abdul Haqq to place the biographies of Sufis whose dates were questionable into a reasonable historical sequence, avoiding dates based on unauthentic traditions. He scrupulously excluded all references to supernatural and miraculous elements, highlighting instead the mystical and spiritual ideas, ethical behavior and psychological perceptions of the great Sufis, using authentic mafuzat and the letters and writings of the Sufis themselves. Although a large number of malfuzats have now been discovered, a considerable body of such literature still remains in obscurity and the best source of information still remains the Akhbarul-Akhyar.
The Akhbarul-Akhyar was completed in 996/1588, but revised and completed 3 years later. Some of the sources of information available to the Shaikh are now extinct according to the author S.A.A Rizvi and the work remains an invaluable mine of information for Indian Sufis for the period of Shaikh Muinuddin Chishti (Rdhiya Allah ta'ala anhu) to Shaikh Abdul Haqq's (Radhiya Allah ta'ala anhu) own day.
Shaikh Abdul Haqq Muhaddis Dihlawi translated the famous collection of the sermons of Shaikh Abdul Qadir, entitled the 'Futuh al-Ghayb', into Persian. The translations went a long way to popularizing the teachings of the Qadiri and published several times in India. Shaikh Abdul Haqq was a disciple of Shaikh Muhammad Musa Qadiri and Shaikh Abdul Maali Qadiri [may Allah be pleased with them all].