Question: What is the ruling on someone who testifies: “Laa ilaahaa illaa Allaah (there is no god but Allaah) and Muhammad is the Messenger of Allaah,” performs Salaah (Prayer) and all the other religious obligations, but, when they are angry or in a discussion with a certain person, they say some words that I am ashamed to mention or say, except in this type of situation that necessitates me to do so to explain the situation. The things that are said are such as: “Damn your Lord’s Religion” and other similar phrases. Is someone who says such things obliged to perform Ghusl (a ritual bath) and are their deed nullified? Please explain this matter to us.
Answer: What you mentioned about the person saying: “Damn your Lord’s Religion,” this takes them out of Islaam. It is obligatory that they should be advised and guided with wisdom, good advice, and the best arguments, so Allaah may guide them and they will stop saying such things in the future… read more here.