The mishnah before us deals with a man who was married to two women and sold his field. The field was mortgaged to both marriage contracts, but its value was not enough to pay both of them, only one marriage contract.
The first case - two wives and one buyer:
Both women were married before the sale, and therefore their claim on the field remains even after it was sold, and they may collect it from the buyer. However, the woman who married first takes precedence over the second in collecting, since payment of her marriage contract came first.
In this situation, for whatever reason, the first wife writes to the buyer that she has no claim against him, and that she has no intention of contesting his purchase and taking the field from him. From here on, matters go around in a circle:
The second wife, who wrote nothing to the buyer, collects the field from him, since her marriage contract too preceded the sale.
The first wife, whose right takes precedence over the second's, takes the field away from her.
The buyer takes the field away from the first wife, on the strength of the commitment she wrote him that she would not contest his purchase.
And once again the second wife comes and collects from the buyer - and so it goes on and on.
The result is that the parties go round and round in an endless circle, until they reach a compromise among themselves - a compromise that everyone can agree to, even though it does not fully satisfy anyone.
The second case - a creditor and two buyers:
The mishnah establishes that the same law applies, in the same formulation and the same structure, in the following scenario as well: a man owes his fellow one hundred dollars, and his field, worth one hundred, is mortgaged to the loan. He sold half the field for fifty to one person, and afterwards the second half for fifty to another person. The sale was made with a guarantee, so that if the field is seized from the first buyer, he can collect from the second buyer and take his field from him.
The creditor is entitled to collect both fields, since his debt is one hundred and each field is worth only fifty. Even so, he writes to the second buyer that he does not intend to contest his purchase. And so matters go around:
The creditor first collects the field from the first buyer, to whom nothing was written.
The first buyer, who lost his field, takes the field from the second buyer, because he takes precedence over him.
The creditor comes and collects this field from the first buyer.
The second buyer takes it from the creditor, on the strength of his commitment not to contest his purchase.
The first buyer again takes it from the second buyer - and so it goes on and on.
Here too matters go around in a circle, until the parties arrive at a compromise.
The third case - one wife and two buyers:
The mishnah concludes that the same law applies even when there is only one wife: her marriage contract is one hundred, and her husband sold two fields worth fifty each, in the same manner explained in the previous case. The wife writes to the second buyer that she will not make a claim against him, and from here the circle begins to turn:
The wife collects a field worth fifty from the first buyer.
The first buyer collects from the second buyer.
The wife comes and collects again from the first buyer.
The second buyer takes it from her - and so it goes on and on.
They too go round and round, until they reach a compromise among themselves.
In summary: in all three cases - two wives and one buyer, a creditor and two buyers, and one wife and two buyers - a circular claim is created: the waiver written to one of the parties causes each one to take from the other over and over again, and there is no end to the cycle of claims, until the parties reach a compromise acceptable to everyone.