What is the ruling on taking money without right and using it in a profitable project, then returning it to its owner, knowing that there are circumstances and a dire need for marriage?

It is not permissible for anyone to take another's money under the pretext of need. A need that does not reach the level of necessity does not permit this, and whoever does so is sinful and liable. As for someone who took another's money and traded with it, he must repent and return what he took. Scholars have differed on whether he must return the profits along with the stolen amount, or if returning only the principal is sufficient.