Interest

Q: My father gave some money to a broker for land so some how my father can't get the land so the broker said that he will return the amount which he has took from us but after 1 year he gave some amount from the total amount. After that my father told him why don't you return all my money but he said that he couldn't give the full amount at once because he used the amount in his business. But he said (if we don't demand it) he will return our money with interest of 2.5%. So my question is, is it permissible to take the extra 2.5%?

Discharge from the back passage

Q: I have these problem. Sometimes when I release gas I have some white fluid come out of my back passage. Sometimes it is not possible to wash my back at work as there are no proper jugs to use so I just wipe it dry using tissue. I understand you must use flowing water to wash of the stool. My question is if there is no smell or physical trace of faeces are my underpants deemed still to be pure? I don't smell anything on them, I can't ascertain whether the colour of the stool gets on my underpants as they are dark colours. But there is no smell or physical stool there.

Non-Muslim donating money towards the building of a Musjid

Q:

1) If a non-muslim ( hindu or christian, etc ) gives money towards the building of a mosque, is it acceptable?

2) If the whole project of building a mosque has been financed by a non-muslim, can we pray in such a mosque? Will our prayers be acceptable?

3) If a non-muslim has financed the building of a madrasah, or some classes of that madrasah, is that acceptable? Can our children learn there?