Sergeant

Ibn al-Qayyim (may Allaah have mercy on him) said:
Zina encompasses all the characteristics of evil:
Lack of religious commitment,
Loss of piety,
Loss of chivalry,
Lack of protective jealousy (gheerah)
You will not find any adulterer who is pious, or keeps his promises, or speaks truthfully, or is a good friend, or has complete protective jealousy towards his family.
Treachery
Lying
Betrayal
Lack of modesty
Lack of awareness that Allaah is always watching
Lack of chivalry
Loss of protective jealousy from the heart – these are the effects and implications of zina.
One of the effects of zina is that it earns the wrath of Allaah because His sacred limits are transgressed.
Darkening of the face
Grimness and misery of face that are apparent to other people.
Darkness of the heart and the extinguishing of its light (which is what causes the extinguishing of light in the face and the darkening thereof.)
It leads to poverty
Loss of respect & the lowering of his status in the eyes of his Lord and in the eyes of His slaves.
You lose the best of attributes, namely chastity, goodness and righteousness, and it earns him their opposites, namely immorality, evildoing, adultery and betrayal.
He will feel uneasy and distressed, for adulterers are doing the opposite of what they are seeking.
You lose the title of believer, as it was narrated in al-Saheehayn that the Prophet (peace and blessings of Allaah be upon him) said: “No adulterer is a believer at the moment when he is committing adultery.”
Alienation which Allaah instills in the heart of the adulterer, and this is like the alienation that shows on his face.
Lack of respect, as his family, friends and others lose respect for him, and he becomes the most despicable thing in their sight; this is in contrast to the chaste person, who is blessed with dignity and sweetness.
People will regard him as a traitor and no one will trust him with regard to his wife or child.
The foul odour that will emanate from him and be detected by everyone who has a sound heart; it will emanate from his mouth and body, and were it not for the fact that there are all the people have a similar odor, that smell would spread far and wide.
He has exposed himself to missing out on the delights of al-hoor al-‘iyn in the beautiful abodes of the Garden of Eden (Jannaat ‘Adan).
Allaah has forbidden Paradise to every evil person, and He has made Paradise the abode of the good, and no one will enter it but those who are good. Allaah says (interpretation of the meaning):
“Those whose lives the angels take while they are in a pious state (i.e. pure from all evil, and worshipping none but Allaah Alone) saying (to them): Salaamun ‘Alaykum (peace be on you) enter you Paradise, because of that (the good) which you used to do (in the world)”
[al-Nahl 16:32]
“and its keepers will say: Salaamun ‘Alaykum (peace be upon you)! You have done well, so enter here to abide therein”
[al-Zumar 39:73]
So they will deserve the greeting of the angels and admission to Paradise because of their goodness. But the adulterers are among the most evil of creation, and Allaah has made Hell the abode of evil and its people. When the Day of Resurrection comes, the evil will be distinct from the good, and the evil will be piled up together, then it and its people will be thrown into Hell. No one who is good will enter Hell and no one who is evil will enter Paradise.

For the one who is chaste has sweetness in his face and contentment in his heart, and whoever sits with him feels at ease with him. But the adulterer has signs of alienation in his face and whoever sits with him will feel uneasy.

Similarly, those who enjoy forbidden images in this world will also be deprived of such in the Hereafter. Indeed, everything that a person gets in this world, if he indulges in it by permissible means, his share of it on the Day of Resurrection will be reduced to the extent that he indulged in it. And if he got it from haraam sources, he will lose out on it altogether on the Day of Resurrection.

He may seek help to commit zina by means of sihr (witchcraft) and shirk, and he may or not know that this sin inevitably includes other sins committed beforehand or alongside it, and that it leads to other kinds of sins that come after it. It is surrounded by a host of other sins that come before and after. It is the thing that is most likely to bring about evil in this world and the Hereafter, and the most likely to prevent good in this world and in the Hereafter.

“That is so because Allaah will never change a grace which He has bestowed on a people until they change what is in their ownselves. And verily, Allaah is All-Hearer, All‑Knower”
[al-Anfaal 8:53]
“But when Allaah wills a people’s punishment, there can be no turning back of it, and they will find besides Him no protector”
[al-Ra’d 13:10]

These are some of the harmful effects of this action.
Book by Ibn al-Qayyim al-Jawaab al-Kaafi li man sa’ala ‘ala al-Dawaa’ al-Shaafi.