Impure eyes, on the other hand, block our path to understanding it. Rabbeinu Yonah (Avos 1:5) spells this out in no uncertain terms: "With a man's head full of contemptible visions, how can it possibly simultaneously absorb thoughts of Torah? It's one or the other. Those sunken in the pursuit of the uncouthness of this world become insensitive to spiritual beauty. These two opposites cannot sit side by side in the same heart." The choice is ours.
The Ben Ish Chai (Parshas Bo, shana 1) warns of an evil spirit (klipa) who shadows us and tries to wipe our Torah studies clean off our minds. The way to thwart his harmful activities is to preserve the kedusha of our eyes.
Rav Yosef and Rav Sheishess were the best at remembering their learning, not in spite of their total blindness, but because of it. Their rebbe, the famous Rav, never glanced beyond his daled amos (Teshuvos Hagaonim 178). When he passed away, they ached to emulate this asceticism but found themselves unable to maintain it. And so they willingly accepted blindness. L'havdil, even secular sources maintain that beholding and visualizing sinful things will, in time, damage the memory, (Machzeh Einayim pg. 9).
One of the most handsome men ever was Yosef Hatzaddik. Breathtakingly beautiful, his name is also synonymous with unblemished holiness in the face of agonizing trials.
The drama of Yosef's story begins to unfold when he is only seventeen years old. Suddenly, he finds himself torn away from the sheltered environment of his parental home, wrenched from all his illustrious family. Alone and among uncaring masters, miles away from his loving father who is inconsolably mourning him as dead, he is brought down to Mitzrayim - a land steeped in immorality.
Here, he was sold as a slave to the wealthy and prominent Potiphar who quickly promoted him to stewardship over all his enterprises and home affairs. Potiphar, not slow in appreciating the blessing of having this gifted manager around, soon put everything into those capable young hands and allowed himself to sit back.
His wife, however, sat up. The unsurpassed beauty of this newly arrived slave piqued her interest. She observed how implicitly her husband trusted him to carry out tasks in her very own home.
Inexorably, her mind became obsessed with the sole goal of somehow getting Yosef to sin. She noted, however, a technical problem. His eyes were always averted, making the ultimate statement, "Not interested." Undeterred, she tried verbal persuasion.
Then she started changing her attire three times a day. Rather pointless, of course. How could she hope to captivate a boy who never looked at her? But this formidable temptress, relentlessly enticing Yosef to yield to her advances, was implacably determined to somehow get him to look at her, even just once (Midrash Rabbah, 7:10).
So she stepped up the pressure, making life successively harder for him, threatening his refusals with the direst reprisals. She positioned a skewer right at his throat to coerce him to look in her direction, just to save himself from danger.
It was all in vain. Yosef remained impervious, steellike, immovable, aloof, brimming with love for his Creator. From the Midrash it's apparent that, of all his trials - trials way beyond the endurance limits of later generations - the hardest nisayon that Yosef had was that of guarding his eyes. Yosef calmly and conscientiously continued carrying out his duties, until that cruel woman, her every design thwarted by his unbending "no", had him thrown into prison on charges of attempting to seduce her, his master's "innocent" wife.