It is related on the authority of A'isha that the Messenger of Allah said:
One who has mastered the Quran shares the rank of the noble, pious scribes. While one who recites the Quran falteringly, who finds it difficult to recite, for such a one there is a two-fold reward.
This Hadith was related by Bukhari, Muslim, Abu Dawud, and Tirmidhi.
Teachings: The Irrelevance of Pleasure in Matters of Worship
Sometimes people find that they are not deriving any pleasure from the act of remembrance of God (dhikr), or the performance of other acts of worship, which makes them become discouraged and they stop doing those things altogether. Sometimes they become so disheartened that they begin thinking that what they were doing was in vain and essentially futile. Such misgivings damage spiritual development because " confidence " is the key to all such development.
The spiritual teachers explain that the object of dhikr is not pleasure. They say maintaining one's level of involvement in dhikr, even when it is not enjoyable, is of more benefit than gaining pleasure. Therefore, a lack of pleasure is not necessarily indicative of a corresponding lack of benefit. Rather, the opposite is true.
The above Hadith explains the counterintuitive aspect of why there is a double reward for the person who struggles in reciting the Qur'an than for one who finds it easy to read the Quran.
Adapted from "A Sufi Study of Hadith" by Maulana Ashraf Ali Thanawi. Translated by Shaykh Yusuf Talal Delorenzo