What is the ruling on someone who sees a beautiful woman and desires to have intercourse with her, and cannot stop himself from this habit?

Allah Almighty commanded the believers to lower their gaze and guard their private parts, because that purifies their hearts and souls, in affirmation of His saying: ﴿Tell the believing men to lower their gaze and guard their private parts. That is purer for them. Indeed, Allah is Acquainted with what they do.﴾ [An-Nur: 30].

Indeed, the gaze is the greatest door to the heart, and it is obligatory to lower it from all forbidden things and everything from which temptation is feared. The Prophet, peace and blessings be upon him, clarified the right of the road by lowering the gaze, refraining from causing harm, returning greetings, enjoining good, and forbidding evil, and he forbade following one glance with another.