Taking a false oath
Q: I smoked weed once or twice which I am not sure is haraam or not. Anyways recently my mother found it out from my bag. It wasn't mine and she made me swear upon her head and the quran that I haven't ever smoked weed in my life and I did. Please tell me did I do wrong by taking a false oath and what penalty I have to pay for forgiveness? If I hadn't done it, she might be heartbroken.