[A Man Gave Another a Sum of Money to Trade With, and Lent Him Half of It]

Answer—and Allah is the granter of success: It does not appear to me that this arrangement falls under the heading of a loan that draws a benefit—which is a form of usury—because the benefits that the capital owner obtains are from the profits and returns of his capital, which constitutes half of the amount advanced.
If it is said: The loan is conditioned upon the borrower trading with both his portion and the lender’s portion, with half the profit going to the lender.
We say: That benefit is shared by both parties, because when the capital increases, profits increase and multiply.
To clarify: A man may find a large, profitable lot of goods and desire to purchase it while possessing only half the price. He then seeks someone to provide the other half of the price, who will receive half the profit without doing any work with him. When profits are realized, they are divided in halves. There is no problem with the validity and permissibility of this, and this example illustrates the validity and permissibility of the arrangement we mentioned.
If it is said: The one advancing the funds only lent half of them to the worker so that he would trade the other half for him and give him his profit outright, without the worker receiving any commercial benefit in return for his work.
We say: Both parties benefit—each has half the profit from the advanced funds; they are equal in benefit. This arrangement is exactly like muḍārabah (silent partnership), except that the capital owner lent the worker half of the advanced capital for a benefit returning to both parties—namely, that the worker will be more attentive and careful in his trade and dealings if he knows he will share in any loss.
And the People of the House (Ahl al-Bayt) have said—as in Sharḥ al-Azhār and its marginalia—that when the two benefits are equal, meaning the benefit to the lender and the benefit to the borrower, the loan is permissible and valid. This is the gist of what is there, and Allah knows best.
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2