Salam Alaykum shaykh. I have a friend ho have accepted islam not long ago. He asks if it is allowed for him that his father who is not a muslim, buys a house With a loan based on ribaa. And then my friend will buy the house from his father by monthly installement,wihtout ribaa?

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.

It is not permissible for your friend to urge his father or to help him to borrow money with Riba (interest and/or usury), as Allaah Says (what means): {…but do not help one another in sin and transgression.} [Quran 5:2]

However, if your friend's father indeed buys the house with a loan with Riba, then he is the one who is sinful but it is not forbidden to benefit from the house, and it is permissible to deal with him in regard to this house in a permissible transaction, like buying it from him by installments and the like.

For more benefit, please refer to Fataawa 84127 and 85569.

Allaah Knows best.