بسم الله الرحمن الرحيم
We begin with Allah’s blessed name, we praise him and we glorify him, seek his forgiveness and ask him to guide us. Whoever Allah guides, None can lead astray and whoever he misguides, None can guide. There is no power and no strength except from Allah, The most high, the Most great, the most powerful. We bear witness that there is no one worthy of worship but Allah Alone, and we bear witness that Prophet Muhammad (pbuh) is His slave-servant and the seal of His Messengers. We pray for peace and blessings on all the noble messengers and in particular on the last of them all “the blessed prophet Mohammad (pbuh)”
O Believers!, fear Allah and give up that 'riba' which is still due to you, if you are true believers. But if you do not do so, then you are warned of the declaration of war against you by Allah and His Messenger! QURAN [2:278]
When Islam has declared something forbidden, then to derive any income from such an establishment would also be forbidden.
Narrated by Ali ibn AbuTalib Ali heard Allah's Messenger (saws) invoke the curse of Allah on those who took usury, those who paid it, those who recorded it, and those who refused to give sadaqah. Al-Tirmidhi 
Thus it would be absolutely forbidden or haram for a believer to work in the conventional banks whose primary business is dealing with interest or riba. However, there is absolutely no harm in working in a bank that works on the principles of Islam. These types of banks are called Islamic banks.
Narrated by Anas ibn Malik Allahs Messenger (saws) said: 'The seeking of knowledge is obligatory for every Muslim.'. Al-Tirmidhi [Hadith 218]
The absolute majority of scholars are of opinion that it absolutely obligatory to achieve the basic knowledge of Islam.
Allah says in the glorious Quran: Whosoever adopts the righteous way, his righteous conduct will be for his own good; and whosoever goes astray, his deviation shall brings its consequences on himself. No bearer of burden will bear the burden of another. And We do not inflict punishment until We have sent a Messenger (to the people). Quran [17:15]
It is the promise of Allah that he will not punish anyone who has not received the message, but here the message was received by your father, as he was a Muslim, and on a Muslim it is absolutely obligatory to receive the basic knowledge of the beautiful deen of al-Islam. Not receiving the message cannot be an excuse for a Muslim.
Dear brother, If one has in ones ignorance consumed riba , and has realized ones crime and is ashamed of what he has done in ones past and seeks sincere repentance from one lord and has promised ones lord that he would never ever again deal with it, then know that our lord is most merciful and oft-forgiving, he forgives any sin he wishes.
Allah says in the glorious Quran: (O Prophet) say: “O My servants who have wronged their own souls….Do not despair of Allah’s Mercy! Surely, Allah forgives all sins. He indeed is the All Forgiving, All Merciful. Return to your Lord and submit to Him before the scourge overtakes you; for then you may get no help from anywhere.” Quran [39:53-54]
Narrated by Abu Sa'id Allah's Messenger (saws) said that the Shaytaan said, "By Thy Might, my Lord, I shall continue to lead Thy servants astray as long as their spirits are in their bodies!" The Lord, Who is Great and Glorious, replied, "By My Might, Glory and Exalted Station, I shall continue to pardon them as long as they ask My forgiveness!" Al-Tirmidhi  And Allah alone knows the best.
I ask Allah to make this a sincere effort, seeking his pleasure, and I ask him to grant us refuge in him from the evils within ourselves, and that in our deeds. I ask him to grant us success in achieving whatever pleases him; And May Allah Shower His blessings and mercy upon our beloved Prophet Muhammad (pbuh), his family and his Companions and on all those who follow him until the final hour.Ask Your Question