Reference: http://www.alfawzan.af.org.sa/node/15380
Question: Is it permissible for me to supplicate against someone who has oppressed me in a major way, thereby cutting-off my sustenance – and I’m only a young man who wants to get married – and [here I am] living this life?
Response: In the name of Allaah, All Compassionate, All Merciful. All Praise is due to Allaah, Lord of the worlds, and may the prayer and salutation [of Allaah] be upon our Prophet Muhammad, and his family and all of his companions.
Supplicating against the oppressor is permissible, however, forgiveness and overlooking [his misdeed against you] is the best, and better for you. That is because if you supplicated against him, then [by doing so] you have taken your right from him. As for your claim that he cut-off your sustenance, then this statement is incorrect. The sustenance which Allaah has decreed for you can never be cut-off by anyone; so if this is the sustenance [which Allaah has decreed] for you, then it cannot be cut [by anyone]. So you must place your [complete] trust in Allaah (‘Azza wa Jall).
