Shaykh al-Islām—may Allah sanctify his soul—said:

Section: A Principle Concerning Property Received under an Invalid Contract

There are two possibilities: either the contracting party considers the contract invalid and knows it to be so, or he does not consider it invalid.

In the first case, he is like someone who wrongfully seizes another’s property, since he has taken possession of something he knows he does not own. Yet, because the contract provides a semblance of entitlement and possession was taken by mutual consent, does he acquire ownership by taking possession, or not? Or should a distinction be drawn according to whether or not he has undertaken further transactions involving it? This is the well-known disagreement concerning ownership: is it acquired by taking possession under an invalid contract?

As for a contracting party who considers the contract valid, an example is that of non-Muslims under Muslim protection who conclude contracts among themselves that are forbidden in Islam, such as sales of wine and pigs, and usurious transactions. If possession is taken under these contracts before they embrace Islam or seek adjudication from us, the contracts are upheld for them, and they own what they have received under them, without dispute. This is based on the words of Allah Most High:

“O you who believe, fear Allah and give up what remains of usury, if you are