His father, Maulana Zahurul Haq was a notable student of Ashraf Ali Thanwi and graduated in Hadith studies from the Darul Uloom Deoband in 1335.

His elder brother, Ahmadul Haq, collected old books and was the owner of a store known as the Ashrafiyyah Kutubkhana, which opened in Zindabazar, Sylhet not long after the Independence of Bangladesh in 1971.

[2] Obaidul Haq started his career as a teacher in joined Dhaka's Hossainya Ashraful Ulum Madrasa near Bara Katra from 1949, teaching hadith studies.

He returned to Bengal in 1954, joining as a teacher at the Dhaka Alia Madrasa, where he taught hadith studies between until 1971 and served as the additional vice principal from 1973 through 1979.

At a conference on 1 April 2005, organised in Paltan Maidan, Dhaka by the Jamiat-e-Ulema-e-Islam he along with the leading ulema of India, Pakistan and Bangladesh declared a fatwa denouncing terrorism.

[5] In 1994, he expressed concern over the growing support for the unfair practices of Christian proselytizers by non-governmental organisations and the sympathy for them by Bangladeshi left-wing political parties.

[6] On 21 March 2003, he led a large anti-war rally in protest of the invasion of Iraq with Fazlul Haque Amini, where he remarked that: The US will occupy all the oil-rich Middle East and Muslim countries, including Saudi Arabia and Kuwait, gradually.