Ibn al-Qayyim (RH):1 – It is obedience to the command of Allaah, which brings happiness to man in this world and in the next.
2 – It prevents the poisoned arrows (of the shaytaan), which may lead to his doom, from reaching his heart.
3 – It creates a heart that is devoted to and focused on Allaah. Letting the gaze wander distracts the heart and keeps it far from Allaah.
4 – It strengthens the heart and brings it peace, just as letting the gaze wander weakens it and makes it sad.
5 – It brings light to the heart, just as letting the gaze wander brings darkness to it.
6 – It generates true insight which can distinguish between truth and falsehood, sincerity and lies.
7 – It creates a heart that is steadfast, brave and strong.
8 – It blocks the shaytaan from a means of entering his heart
9 – (Not doing so) distracts one away from thinking of what is in one’s best interests, so his affairs become neglected and he follows his whims and desires and neglects to remember his Lord.
10 – Between the eyes and the heart there is a connection which means that the one is affected by the other, and if one of them becomes good, the other will also become good, and if one becomes corrupt the other will become corrupt.
— al-Jawaab al-Kaafi (125)