Is it unlawful for me to accept my father's financial support if it originates from usurious dealings, and what should I do in this situation? Is my Hajj, which was financed by my father, valid? Is it permissible for me to go with him to perform Umrah? If a suitor proposes to me, and his father deals in usury, yet the suitor himself is convinced of its unlawfulness, should I accept him, knowing that his father will assist him with the marriage expenses? Can I remain in my current situation, estimate what was spent on me and on the marriage, and then have my husband donate the equivalent of the usurious interest to charity?

Ruling on dealing with a father's money if he engages in usury (riba):

What the father does by engaging in usury is forbidden, and it is the very essence of forbidden usury. Whoever issues a fatwa permitting it has deviated and erred.

Not all of the father's money is forbidden. His principal capital is permissible, and what is forbidden are the usurious interests. So, his money is mixed with permissible and forbidden elements.

Dealing with someone whose money is mixed, through buying, selling, gifting, and other transactions, is not forbidden. Indeed, the Prophet, peace and blessings be upon him, and his Companions, used to deal with Jews, despite them being people of usury. However, it is stipulated that the transaction must not involve the very essence of forbidden money.

There is no harm for you in eating from your father's provision, or benefiting from his funding for Hajj, Umrah, marriage, and so forth, unless you know that a specific item came to you directly from forbidden money.

The same applies to a suitor whose father engages in usury.

If you can do without money from someone whose wealth is mixed, that is preferable, because dealing with someone whose money is mixed is disliked in the madhhab of the majority of scholars.