His wife committed zina twice with a Christian man; should he divorce her? If she apostatises will there be any sin on him?
Question

                A man want to divorce his wife after she committed adultery for the second time with a christian man. He had forgive her the first time and now after she had travelled , she had committed adultery for the second time with another christian man but the husband this time want to divorce her because he is an Islamic teacher and he fears for his reputation. But he fears if he divorce this woman she will leave Islam and go back to Christianity and also she does not want to wear hijab but pray and fast . they have grown up children. Please advise The husband does not want to be responsible for the wife leaving Islam.
Praise be to Allah.
      Firstly: 

    If a woman persists an immoral action and does not repent 
    from it or give it up, even if the matter did not go as far as zina, such as 
    if she had a relationship with this Christian man or anyone else, then it is 
    not permissible for the husband to keep her, because that is a kind of 
    cuckoldry (diyaathah), and cuckoldry is a major sin, because of the report 
    narrated by al-Nasaa’i (2562) from ‘Abd-Allah ibn ‘Umar (may Allah be 
    pleased with him) who said: The Messenger of Allah (blessings and peace of 
    Allah be upon him) said: “There are three at whom Allah, may He be glorified 
    and exalted, will not look on the Day of Resurrection: the one who is 
    defiant towards his parents, the woman who imitates men, and the cuckold.”

    Classed as saheeh by al-Albaani in Saheeh al-Nasaa’i. 

    The cuckold is the one who approves of evil conduct in his 
    family. 

    Shaykh al-Islam Ibn Taymiyah (may Allah be pleased with him) 
    was asked about the one who came into his house and found a stranger with 
    his wife, so he gave her her dues and divorced her by talaaq, then he went 
    back and reconciled with her and heard that she had been found with a 
    non-mahram man.  

    He replied: In the hadeeth from the Prophet (blessings and 
    peace of Allah be upon him) it says that when Allah, may He be glorified and 
    exalted, created Paradise, He said: “By My glory and majesty, no miser, liar 
    or cuckold will enter you.” The cuckold is the one who has no protective 
    jealousy or pride. In al-Saheeh it is narrated that the Prophet 
    (blessings and peace of Allah be upon him) said: “The believer has 
    protective jealousy (gheerah) and Allah has protective jealousy, and the 
    protective jealousy of Allah is that no slave should do that which is 
    forbidden to him.” And Allah says (interpretation of the meaning): “The 
    adulterer — fornicator marries not but an adulteress — fornicatress or a 
    Mushrikah; and the adulteress –fornicatress, none marries her except an 
    adulterer — fornicater or a Mushrik [and that means that the man who agrees 
    to marry (have a sexual relation with) a Mushrikah (female polytheist, pagan 
    or idolatress) or a prostitute, then surely, he is either an adulterer — 
    fornicator, or a Mushrik (polytheist, pagan or idolater). And the woman who 
    agrees to marry (have a sexual relation with) a Mushrik (polytheist, pagan 
    or idolater) or an adulterer — fornicator, then she is either a prostitute 
    or a Mushrikah (female polytheist, pagan, or idolatress)]. Such a thing is 
    forbidden to the believers (of Islâmic Monotheism)” [al-Noor 24:3]. The 
    correct scholarly opinion is that it is not permissible to marry a zaaniyah 
    (a woman who commits fornication or adultery) until after she has repented. 
    The same applies if the wife commits zina: the husband has no right to keep 
    her in that case; rather he should leave her, otherwise he will be a cuckold 
    (duyooth). End quote from Majmoo‘ al-Fataawa, 32/141

     Secondly: 

    If the woman has repented, turned over a new leaf and is 
    living a righteous life, and she has cut off all ties to that non-mahram 
    man, then the husband may keep her, and perhaps Allah will reward him for 
    treating her kindly and concealing her sin. 

    We have stated that it is not permissible for him to keep her 
    as his wife if she committed zina and has not repented from it sincerely, 
    and we stated that if she repents and turns over a new leaf, then he may 
    keep her and conceal her sin, if he has the patience to do that. What we 
    have said about it being permissible to keep her if she repents is not 
    obligatory for him, rather it is up to him. In all cases he may leave her, 
    because zina on the part of the wife is extremely abhorrent and most people 
    cannot forgive that. And if he divorces her, then he is not responsible for 
    what she commits of sin, and if she apostatises from Islam, she alone is 
    responsible for that, because she is accountable and of sound mind: if she 
    does good deeds that it is in her favour and if she does bad deeds then it 
    counts against her. 

    We ask Allah to protect the Muslims from all trials, evils 
    and turmoil. And Allah knows best.