What is the evidence from the Quran or Sunnah for the prohibition of looking with lust at those whom it is not ordinarily forbidden to look at?

Allah commanded lowering the gaze from women and vice versa, to prevent corruption and the arousal of lust leading to indecency. Gazing is the origin of most incidents; it generates a fleeting thought, then an idea, then desire, then intention, then resolve, and finally the action occurs. The jurists agreed on the prohibition of any gaze that leads to the arousal of lust. They emphasized the prohibition of gazing at an amrad (a beautiful boy) due to the potential for attachment and desire, as happened with the people of Lut. The imams unanimously agreed on the prohibition of gazing at an amrad with lust, and the majority of them forbade it when there is a fear of lust being aroused. Some even forbade it absolutely. Imam al-Nawawi said: "Likewise, it is forbidden for a man to gaze at the face of an amrad if he is handsome, whether with lust or not, and whether one is safe from temptation or fears it. This is the sound and preferred view among verifying scholars." Shaykh al-Islam Ibn Taymiyyah said: "Gazing at the face of an amrad with lust is like gazing at the face of one's mahram (unmarriageable kin) or a foreign woman with lust." He also mentioned that whoever repeatedly gazes at an amrad and claims they are not gazing with lust has lied. Therefore, gazing at beautiful images with lust or when there is fear of lust being aroused is forbidden.