Q: If I invest in a partnership with other parties, do I need to verify whether their source of finance is Halal?
الجواب حامدا ومصليا ومنه الصدق والصواب
A: If you have reason to believe that their source of funding does not conform to Sharī‘ah then you must actively ascertain as to whether that is indeed true. If you have no way of knowing the identity of other investors and their source of funding then it is best to refrain from investing in such projects. Normally, guaranteed returns do not conform to Sharī‘ah.