What is the ruling on depositing a sum of money in a bank that allows it to be withdrawn to participate in a draw for one million Saudi Riyals, and is it obligatory to give out a sum to purify this money if it was originally lawful?

We have previously explained that bank draws are a form of prohibited gambling (maysir) and an interest-based loan (riba). Therefore, it is forbidden for a Muslim to engage in this act. If one does engage in it and obtains money from it, it is not permissible for him to own it. Rather, he must spend all of it on the general welfare of Muslims.