He has an illicit relationship thinking that his prayers will cover up his sin
25-11-2011 | IslamWeb
Question:
My husband is 55 yrs old and we have been married for 18 yrs.Recently he has started living with a non-muslim filipino women( they are not married) but he still prays 5 times daily , even reads the Quran, prays tahajud & also attends islamic programmes.He also understands that whatever he is doing is wrong and he thinks his prayers will cover up his sins & after suffering for sometime in hell he will return to heaven since he is a muslim.So whatever he is thinking about judgement is it really correct according to the Quran?
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad 
is His slave and Messenger.
If it is true that your husband has an illicit relationship with that woman, then he is very wrong, and he is doing an act of the people of the Pre-Islamic Era of Ignorance which Islam has prohibited. Allaah Says (what means): {… not unlawful sexual intercourse or taking [secret] lovers.}[Quran 5:5]
Therefore, he must take the initiative to sincerely repent to Allaah while fulfilling all the conditions of a sincere repentance which are clarified in Fatwa 86527.
Your husband should know that among the most important benefits of the prayer is that it prevents its doer from shameful and unjust deeds. Allaah Says (what means): {Indeed, prayer prohibits immorality and wrongdoing, and the remembrance of Allaah is greater. And Allaah knows that which you do.}[Quran 29:45]
The fact that the prayer wipes out the sins is correct but the prayer, and other acts which wipe out the sins, will wipe out only the minor sins. As regards the grave major sins, then they cannot be wiped out except with sincere repentance. Shaykh Ibn ‘Uthaymeen 
said: “The grave major sins are not wiped out by good deeds; rather, it is only sincere repentance which may wipe them out.”
In addition to this, how can he know that his prayer has been accepted? Indeed, a believer does an act of worship while fearing that it might not be accepted from him; Allaah Says (what means): {And they who give what they give while their hearts are fearful because they will be returning to their Lord.}[Quran 23:60]
Moreover, it is confirmed that ‘Aa’ishah 
asked the Prophet about the above verse and said: "Is it the ones who drink alcohol and steal?” The Prophet replied: "No, O daughter of As-Sideeq [i.e. Abu Bakr]; rather, they are those who pray, fast and give in charity while they fear that it (their deeds) will not be accepted from them, and they are those who hasten to do good deeds.” [At-Tirmithi and Ibn Maajah]
So, the matter of a believer is that he fears whereas the hypocrite feels secure. Al-Hassan Al-Basri said: “A believer is characterized both by fear and doing good deeds, and the hypocrite is characterized both by doing evil deeds and feeling secure.” So, we warn your husband from being conceited.
As regards his statement that he will enter Paradise after suffering for a while in Hellfire, because he is a Muslim, then this is a great deception. How can he know that he will die as a Muslim? Persevering in sin and continuing to transgress the Limits of Allaah and taking His Anger and His severe Punishment as easy matters are one of the reasons that would lead to an evil ending; we seek refuge in Allaah from this.
Furthermore, if we presume that he died upon Islam, and he is thrown to Hell for some time, does he know what Hellfire is. It is confirmed that An-Nu’maan Ibn Basheer 
said: “I heard the Prophet saying: “The person who will have the least punishment from amongst the dwellers of the Hellfire will be a man under whose arch of the feet a smoldering ember will be placed and as a result his brain will boil.” This punishment may continue for a period that would equal the life-span of a person multiplied many folds. Rather, one moment of the punishment of Hellfire would make a person forget all the pleasures of this world. Anas Ibn Maalik narrated that the Prophet said: 'On the Day of Judgment, a dweller of Hellfire who indulged excessively in the pleasures of life, will be brought and dipped into Hellfire and then asked: O son of Aadam, have you ever seen any good? Have you ever enjoyed any pleasure? He replies: Never, I swear by Allaah.” Then on the Day of Judgment, a dweller of Paradise, who was surrounded with troubles in the world, will be brought and put into Paradise and then asked: "Have you ever seen any trouble? Have you ever experienced any hardship? He replies: "By Allaah, I have never seen any trouble and have never experienced any hardship”. [Muslim]
For more benefit, please refer to Fatwa 86263.
Allaah Knows best.