To Retain What You Have Memorized, Revise Often And Consistently
Q. What is the best way to maintain what I have already memorized from the Qur’an?
A. All praise is for Allah alone, and may His prayers and salutaions be upon Muhammad, his family, and his companions.
Constant repetition, truthfulness, sincerity, contemplation, a desire to keep what you have memorized, an understanding of the Qur’an, supplication to Allaah, ask of Him to grant you success in this regard, avoidance of sins, and repentance to Allah for past sins- by employing these means, you will be able- Insha Allah-to maintain what you have memorized.
And success lies with Allah ta’ala. Oh Allaah, send prayers and salutations upon Muhammad, his family and his companions.
Source: Islamic Rulings Regarding The Qur’an pg.16
Sisters Upon Al-Istiqaamah