Silsilat al-Ahadith al-Sahihah

Abu Huraira (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "Every son of Adam inevitably commits a share of adultery; the adultery of the eye is looking, the adultery of the hand is touching, the heart desires and wishes, and the private part either confirms it or denies it."