According to the Shari?ah, you are an adult and have an independent right to choose your marriage partner. If you made a choice and marry a Muslim person from a different caste or creed, it will be valid even though your father refuses you to marry.
Sister, the above is the Shar’ee rule and principle. We wish to advise you that marriage is a major step in one’s life. It has long lasting implications. It is important for you to consult your seniors and consider their opinions as they are based on experience and wisdom in life. Furthermore, your father’s advise is generally motivated by love and concern.
While we clearly state that Shari?ah does not prohibit marrying a Muslim male of any caste and creed, Shari?ah has considered Kafaat (compatibility). A marriage is a life long commitment between two couples. It is expected of them to lead a life of happiness and harmony. For that, compatibility plays an integral role. If the couples are not compatible due to any reason, then that defeats the purpose of marriage. Non-compatibility may lead to marital problems and divorce. This is a common problem in our society. It is, therefore, important for you to consider your options and opinion of your father. If you are doubtful, then seek assistance through Istikhaara.
Do not disconsider the opposite view in such an important aspect of your life. It may be too late before you regret. Life and time are too dear to be lost due to an irresponsible decision.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai