The Prophet ﷺ said, "The eyes commit zina, the tongue commits zina, the hands commit zina, and the feet commit zina. The private parts then either confirm it or deny it."
حدثنا سليمان قال حدثنا إسماعيل قال أخبرني العلاء عن أبيه
أن النبي ﷺ قال العينان تزنيان واللسان يزني واليدان يزنيان والرجلان يزنيان يحقق ذلك الفرج أو يكذبه
Its chain of transmission is sahih. It has already appeared under number 8520, and with similar wording Muslim narrated it in 4/2046, number 2657, in the chapter on divine decree, worded, "The share of adultery has been decreed for Ibn Adam." He said in Majma, 6/256, "Its chain of transmission is jayyid."