In many countries around the world particularly in Muslim majority nations, gambling is generally not practiced by religious people. In fact, in some countries it is even prohibited. The belief is that the easy money obtained through gambling is transient and can lead to various challenges or negative consequences. This is what I have heard thus far.

It's a really difficult question because what is considered normal varies greatly and there may be a minority or even a big number of people who view it as a sin. Imo it's not bad unless it becomes an addiction and puts you in a financially difficult situation. However, if you can maintain control over it, are aware of your actions, and it doesn't negatively affect your family, yourself, or anyone else in your life then it should be fine.

I am somewhat neutral in this situation and I don't believe the father is wrong for standing by his beliefs, especially since it's his house. He may not want to introduce the potential negative impact of 'easy money' from gambling into their lives which could be influenced by religious considerations.

In my country, there is a saying that translates to 'Gambling money does not bear fruit,' implying that money earned through gambling is unlikely to bring any positive outcomes. Considering the father and son's situation, if the father continues to insist on not accepting the money, one possible solution would be to donate it to the poor and needy imho.