This Hadith mentions the merit of those who commit the Qur’an (whole or part thereof) to memory (Huffaz). The word ascend here means to rise in ranks in the Jannah. The more one remembers the Qur’an, the more clear and distinct is his recitation of it, the higher would be the status that he will go on attaining through its blessings. Thus, this Hadith provides inducement for the remembrance of the Qur’an and tells us that its frequent recitation is a means to attain higher ranks in Jannah.
(Riyad Us-Saliheen, Book of Virtues, Chapter 180, No. 1001)