Is it obligatory to look after my wealthy father monetarily who deals in Riba knowingly. while he willingly accept money sent by me for his expenditure.

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.

If your father is wealthy, then, it is not due on you to spend on him. But, at the same time, you should maintain kinship ties with him by giving him money even if he is not in need of it, as a way of perfecting your dutifulness and good treatment to him. It is also due on you to advise him in a kind and lenient manner to refrain from Riba and fear Allaah The Almighty. If he does not accept advice from you, you may then ask the help of some Du‘aah (callers to Islam) to admonish him and remind him of Allaah, perchance he would repent at their hands. Do not despair of his repentance, nor lose hope of calling him to guidance and righteousness, and giving up Riba, keeping in mind the necessity of abiding by kindness and lenience while advising him. That is because the status of fatherhood is great in Islam, so if it is due on one to advise his father to refrain from sin, this should not make it permissible for him to mistreat him or raise his voice at him.

Moreover, if your father sees to what extent you are compassionate towards him and concerned about his righteousness, and how you love good for him and are affectionate to him, he would be touched and would accept your advice, and refrain from Riba; and that is one of the greatest forms of being dutiful to him. For further information, see Fataawa 82254 and 84942.

Allaah Knows best.