Matt 5:28 But I say unto you, That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart.
Gen 3:6 And when the woman saw that the tree was good for food, and that it was pleasant to the eyes, and a tree to be desired to make one wise, she took of the fruit thereof, and did eat, and gave also unto her husband with her; and he did eat.The desire to eat the fruit was sufficient to reveal the condition of their hearts. Eating the fruit simply opened their eyes. God asked them "who told thee that thou wast naked?"
Sin is always conceived in the heart before being given birth in the actions.
But every man is tempted, when he is drawn away of his own lust, and enticed. Then when lust hath conceived, it bringeth forth sin: and sin, when it is finished, bringeth forth death. (James 1:14-15)