In short, there is nothing more beneficial for the heart than reading the Quran and with contemplation and reflection. The Quran encompasses all the levels of the travelers, the conditions of the workers, and stations of those possessing knowledge. It is the Quran that generates love, desire, fear, hope, repentance, reliance, pleasure, entrustment, gratitude, patience, and the rest of the different states that are life to the heart and perfection of it. Likewise, it repels all the rebuked characteristics and actions that cause the corruption and ruin of the heart.
If people were to possess a realization of what recitation of the Quran with contemplation contains, they would devote themselves to it at the expense of anything else. When the person reads it with reflection and he comes across an aayah that he is in need of, for the cure of his heart, he repeats it, even if he does so a hundred times or the whole night. Hence, to recite a single aayah of the Quran with contemplation and reflection is better than reciting the Quran to completion without any contemplation or reflection. It is also more beneficial for the heart and more conducive to attaining eemaan (faith) and tasting the sweetness of the Qur‘an.
— Imam Ibn Qayyim
Source: Causes Behind the Increase and Decrease of Eemaan by Shaykh ‘Abdur-Razzaaq al-‘Abbaad pg. 38