to take, as the party originally wronged, an equivalent amount from his property now in the seller’s possession. Likewise, the person who received that additional sum in exchange for his property may, if his property is not returned, take an equivalent amount from that sum.

This possibility applies to any two parties who conclude an invalid sale and exchange possession, if it is held that possession acquired under an invalid contract does not confer ownership. Each party then has property held by the other: namely, whatever the other received from him. If restitution becomes impossible, each may take the equivalent of his entitlement, whether in property of the same kind or of another kind.

Accordingly, consider the unjust additional sums that have come into the possession of this wrongdoer liable for restitution, taken from purchasers’ funds that have become indistinguishably mixed. If he buys something with those funds, transfers ownership of the additional sums to the purchasers, and takes possession of what he bought, the property of theirs that he acquires stands against the additional sums they received, which are due to their rightful owner. Thus, buying from him at the fair market price is not unlawful; how much more so if someone buys from him at a higher price! This differs from accepting something from him gratuitously, which raises another discussion that does not belong here.

Ibn Masʿūd was asked about a man who deals in usury and offers hospitality to someone else. Ibn Masʿūd replied:

“Eat: the enjoyment is yours, and the accounting is his.”

The scholars have discussed this matter, but this is not the place for that discussion.

Several fundamental questions arise here. One is whether possession acquired under an invalid contract confers ownership. Another is whether, when someone disposes of a particular asset in a way that prevents its return in kind, the claim becomes a personal liability owed by him. Or does it remain attached to his property with which that asset has become mixed, and to that which he exchanged