Hadhrat Shaykh Zulfiqar Ahmad Naqshbandi (db) once narrated the following story while giving a talk: 

Hadhrat Maulana Qasim Nanotwi (ra) once accompanied Hadhrat Maulana Rasheed Ahmad Gangohi (ra) on the journey to Haj. Their was no Hafidh (memoriser) of the Qur’an in their travelling group. During the course of the journey, the Month of Ramadhan came to pass. Hadhrat Maulana Qasim Nanotwi would memorise one Juz (part) of the Qur’an daily and then recite it (as the Imam) during the night in taraweeh. No one realised [that Hadhrat Maulana would memorise one juz every day] and [in this way] he memorised the whole Quran in a short period of one month.

Khutbaat-e-Faqeer, Volume 7, Page 158