"There was a companion of ours in Glasgow who became ill and was hospitalized. He was admitted for three days and on the fourth day the attendant nurse said, "Marry me".
He [the brother in Glasgow] asked, "Why? I am a Muslim, you and I cannot become companions."
She said, "I will become Muslim".
"What's the reason?" it was asked.
She said, "In all my time that I have served in hospitals, except you, I have never seen a man lower his gaze in front of a woman. In my life you are the first person who lowers his gaze when seeing a woman. I come, and you close your eyes. Such great modesty can be taught by none other than a true religion."
The protection of one's gaze entered Islam in her. She testified to the Oneness of Allah (3aza wajal) and became a Muslim. They both got married. By now, the same woman was and is the means of bringing so many other girls and women into Islam.
The Prophet (sal allah alayhi wasalam) considered hungry and lustful looks at a person of the opposite sex as "the zina of the eye," according to his saying, "The eyes also commit zina, and their zina is the lustful look." (Reported by al-Bukhari and others.)
The Prophet (sal allah alayhi wasalam) told 'All ibn Abu Talib, "Ali, do not let a second look follow the first. The first look is allowed to you but not the second.''(Reported by Ahmad, Abu Daoud, and al-Tirmidhi.)