Answered by Shaykh Faraz Rabbani
A Muslim goes into an engineering firm and does not ask its manager how they make their money because it is apparent (i.e. soil and concrete testing). The company may be involved in haram but the Muslim does not ask the manager about the detailed workings of the company and only goes by the apparent outer operation of the company, which is the soil and concrete testing. And since the Muslim knows that all money is halal until proven otherwise, he is content with this job. Would the actions of the Muslim in this case be enough to free him from blame on the Day of Judgment?
Walaikum assalam wa rahmatullah,
As long as the main business of the company is lawful, and one’s own work lawful, then one’s earnings are free of any dubiousness and one’s consciousness should be clear.
And Allah alone gives success.