How do the private parts confirm or deny what the heart wishes or desires?

In the below question asked earlier on this site, https://islam.stackexchange.com/questions/816/what-actions-would-constitute-zina there is this below Hadith: > According to the version narrated by Muslim: > > “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, 2657** I understand the first five types but not the last. Can someone give a tafsir on the meaning of the last statement (in bold)? There is a related question but I see no accepted answer. So not sure on what to accept as per Ijtehad. https://islam.stackexchange.com/questions/55490/what-is-zina-of-the-heart-what-things-constitute-zina-of-the-heart