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, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Any person who dies a Muslim will enter Paradise, even if he goes to Hell first for the sins he has committed. Being a wittol is a great sin because it means he has tolerated adultery in his household. The Prophet, sallallaahu ‘alayhi wa sallam, said that this type of person will not enter Paradise and Allaah the Almighty will not look at him. It was narrated on the authority of Ibn ‘Umar that the Prophet, sallallaahu ‘alayhi wa sallam, said that there are three kinds of people whom Allaah the Almighty will not look at, and among them is the wittol. [An-Nassaa’i]
It was also narrated on the authority of Ibn ‘Umar that the Prophet, sallallaahu ‘alayhi wa sallam, said that Allaah has prohibited a wittol from entering Paradise. [Ahmad]
These Hadeeths have two meanings: one understanding is that such a person will never enter Paradise. This applies to the person who believes this is lawful, despite knowing that it is prohibited in religion. This is because considering adultery to be lawful would make him a non-Muslim, therefore it is prohibited for him to enter Paradise. The other meaning is that such a person may not enter Paradise at first, that is, he would enter Hell first to be punished for his sins, then enter Paradise afterwards, thanks to the grace of Allaah. Still, Allaah the Almighty may forgive him so he does not enter Hell at all, however he will not be among the first to enter Paradise. This applies to all Muslims who die before repenting, but anyone who has repented will be forgiven by Allaah.
Allaah Knows best.