Islam has put a check on all those possibilities which may lead one to adultery and even those actions/deeds of the human body are deemed as adultery, as they may involve one in adultery. There is a Hadith in Musnad Imam Ahmed:
Translation of Hadith: It has been narrated on the authority of Hadhrat Abu Hurairah (May Allah Ta'ala be well pleased with him) that the Holy Prophet (Sallallahu alaihi wa sallam) said: Every part of the body plays its part in adultery. Eyes commit adultery and their adultery is by watching and seeing, hands commit adultery and their adultery is by holding and grasping, legs commit adultery and their adultery is by walking, the mouth commit adultery and their adultery is by kissing. The heart desires and lusts and the private parts confirm it and commit adultery or refuse it and refrain from adultery. (Musnad Imam Ahmed, Hadith No. 8752)
Translation of Hadith: It has been narrated on the authority of Hadhrat Abu Hurairah (May Allah Ta'ala be well pleased with him) said: The adultery of the eyes is to see. (Sahih Muslim, Hadith No. 6925)
Everybody knows that on the day of resurrection (Qiyamah), all human beings will be terribly anxious and will be regretting their past life. In Qiyamah, each eye will be weeping, but as per the glad tidings given by the Holy Prophet (Sallallahu alaihi wa sallam), there will be three eyes, which will neither cry out of fear in Qiyamah nor will shed tears of regret. They are:
1. The eye which refrains from seeing forbidden things.
2. The eye which keeps awake on the path of truth.
3. The eye which sheds tears even to the extent of the head of a fly out of the fear of Almighty Allah.
Translation of Hadith: It has been narrated on the authority of Hadhrat Abu Hurairah (May Allah Ta'ala be well pleased with him) that the Holy Prophet (Sallallahu alaihi wa sallam) said: Every eye will be crying on the day of Qiyamah, excepting 3 lucky eyes:
1. One is that eye, which refrains from (seeing) prohibited things.
2. The eye which keeps awake in the path of truth.
3. That eye, which sheds a tear out of the fear of Allah Ta'ala, even to the extent of the head of a fly. (At Targhib Wat Tarheeb, Vol. 3, Pg. No. 34)