He has repented from zina; does the hadd punishment have to be carried out on him?
Question

                I am married and my wife is in my homeland but I work in a western country in order to earn a living and educate my children. But I committed the sin of zina, and I regretted it and repented to Allaah. Is that sufficient or not? Or must the hadd punishment also be carried out?.
Praise be to Allah.
    Undoubtedly zina is a major sin, and among the means that 
    lead to it are nakedness of women, mixing of men with non-mahram women, the 
    decline in morals and the corruptness of the environment in general. If you 
    committed zina because of being away from your wife and mixing with evil and 
    corrupt people, then you regretted your sin and repented to Allaah 
    sincerely, then we hope that Allaah will accept your repentance and forgive 
    your sin, because Allaah says (interpretation of the meaning): 
“And those who invoke 
    not any other ilâh (god) along with Allaah, nor kill such person as Allaah 
    has forbidden, except for just cause, nor commit illegal sexual intercourse  and whoever does this shall receive the punishment.

    69. The torment will be doubled to him on the Day of 
    Resurrection, and he will abide therein in disgrace;

    70. Except those who repent and believe (in Islamic 
    Monotheism), and do righteous deeds; for those, Allaah will change their 
    sins into good deeds, and Allaah is Oft‑Forgiving, Most Merciful”

    [al-Furqaan 25:68-70]

    And it was narrated from ‘Ubaadah ibn al-Saamit (may Allaah 
    be pleased with him), in the hadeeth about the women’s oath of allegiance, 
    that the Prophet  (peace and blessings of Allaah be upon him) said: 
    “Whoever among you is faithful (to this pledge) his reward will be with 
    Allaah, and whoever does any of these things and is punished, his punishment 
    will be an expiation for him, and whoever does any of these things but 
    Allaah conceals him, then it is up to Allaah: if He wills He will punish him 
    and if He wills He will forgive him.” 
But you have to flee from 
    this corrupt environment that tempts you to sin and seek to earn a living in 
    another country that is less evil, so as to protect your religious 
    commitment. The earth of Allaah is spacious and no one will ever be without 
    a land where he can earn a living and acquire the provision that Allaah has 
    decreed for him. And whoever fears Allaah, He will make a way for him to get 
    out (from every difficulty) And He will provide him from (sources) he never 
    could imagine.