IF A GENTILE LENT [MONEY] TO AN ISRAELITE ON HIS LEAVEN, AFTER PASSOVER IT IS PERMITTED FOR USE. WHILE IF AN ISRAELITE LENT [MONEY] TO A GENTILE ON HIS LEAVEN, AFTER PASSOVER IT IS PROHIBITED FOR USE.
The problem being that leaven belonging to a Jew is renounced before Passover and therefore has no value. This is discussed at length on our page; i.e. whether ownership can be given retrospectively to a time before it was renounced or not.
In addition, there is this interesting passage:
Our Rabbis taught: A shop belonging to an Israelite and its wares belong to an Israelite, while Gentile workers enter therein, leaven that is found there after Passover is forbidden for use, while it need not be stated for eating. A shop belonging to a Gentile and the wares belong to a Gentile, while Israelite workers go in and out, leaven that is found there after Passover may be eaten, while it is unnecessary to state [that] benefit [is permitted].
And also a mishnah which deems that leaven on which a ruin has collapsed does not have to be physically removed, because it is already buried. But it has to be buried three handbreaths deep so that a dog can’t sniff it out!