Business and Dealings

Moving into a house with some stuff of the old owner

Q: I have moved into a new home. The previous owner was not Muslim. He had left some baking trays that fit into the oven that he left here which I presume he was not using. I am not sure if he would have cooked any haraam food with the trays. I wanted to throw his trays away but now some of my baking trays were placed in the same draw and they got mixed up so I don't know which are mine and which are his. Is it fine if I end up using the dishes that he used to cook with as long as its washed with sunlight and water?

Participating in a game named secret sheep for eid which was derived from the game secret santa

Q: Knowing that giving gifts is of great merit and is encouraged in Islam... 

Is it permissible to participate in a game named as secret sheep for eid which people exchange gifts... since it was derived from the name secret santa and the rules etc. all are derived from the secret santa (done on Christmas).

Earnings of a person who works for a company that has some wrong dealings

Q: If I become an electrical engineer and my company takes interest from a bank, will my income be haram? 

If I become an electrical engineer and the company does something haram in a way that they think it's halal (since they don’t know that saying haram is halal is shirk), will I become a disbeliever or sinner for working in that company? 

If my company works with another company that does haram activities or considers haram as halal (since they have no idea that calling haram halal is shirk), then for working in such companies, will I become a disbeliever or sinner? Will my income be haram? Will having the desire to work in such companies make me a disbeliever or sinner? 

If the people in my company are Muslim but they commit shirk or make mockery of Islam, or if they work with companies that do such things — then will I become a disbeliever or sinner for joining those companies? 

And if those companies are at a very high level and offer a handsome salary, will wanting to work there make me a disbeliever or sinner?