If a revert has purchased a new house, his parents are still Hindu. They visit the house for the first time. The mother performs some religious Hindu ritual, the son (revert) knows the reason she is visiting the house, but says nothing. He knows he will not take part in it. He simply does not wish to upset his mother and since he will not take part he does not believe it is worth having an argument with his mother. Should he have told his mum he will not accept any non-Muslim ritual to be performed in his home despite her being hurt?
The son feels an obligation in some way to his parents as they purchased his house for him in cash because he did not want to get a mortgage. He is paying his parents back monthly. They have accepted that he will not part take in any Hindu ritual, however the mother tries hard to keep her religion very much in his life. This does create a strain on the revert's relationship with his practising Muslim wife as she does not wish for any non-Muslim ritual to take part in this house. The wife does not yet live with the revert as the house is being renovated. Please advice.

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. We ask Allaah to exalt his mention as well as that of his family and all his companions.

Islam has given the parents a great status and Allaah paralleled His Right with the right of the parents and made it an obligation on the children to obey them even if they are non-Muslims, Allaah Says (which means): {…give thanks to Me and to your parents, unto Me is the final destination. But if they (both) strive with you to make you join in worship with Me others that of which you have no knowledge, then obey them not, but behave with them in the world kindly,…..}[Quran 31:14]. So you should treat your parents kindly; among the best deeds of being kind to them is to be keen on guiding them to the straight path and make every effort in doing so- being kind and dutiful to them will help you to achieve this objective.

As regards them performing some rituals of their religion in your home, there is no doubt that this is an evil and it is not permissible for you to approve of this matter. The fact that they lent you some money does not make it permissible for you to approve of this evil. However, if you are unable to stop what they are doing, and this is unlikely, and you fear a greater harm, then at least you should not stay in the same place where they perform that evil. It is confirmed that the Prophet said: "Whoever sees an evil, should change it with his hand (i.e. physically); if he can't, then he should change it with his tongue (i.e. verbally); if he can't then he should reject it in his heart (i.e. detest it), and this is the weakest level of faith." [Muslim] The scholars stated that denying evil with in one's heart requires leaving the place where the evil is happening. Finally, it should be noted that the relationship between you and your wife should be maintained at its best, and both of you should avoid any problems as this could lead to unpleasant consequences.  

Allaah Knows best.