Hadith - The categories of Zina

Rasoolullah Sallallahu Alaihi Wasallam said:

“The zina of the eyes is looking, the zina of the ears is listening, the zina of the tongue is speaking, the zina of the hand is touching, and the zina of the foot is walking. The heart wishes and longs and the private part confirms that or denies it.” 

(Muslim)