Mishnah 1:
"Mi shehayah nasui shtei nashim umeis" - a man who was married to two wives and died, and both wives come to collect their kesubah. When the estate contains only a limited sum, not enough to pay both kesubos, which of them takes precedence?
On this the Mishnah rules: "Harishonah kodemes lashniyah" - the wife who was married first takes precedence in collecting over the wife who was married after her.
"V'yorshei harishonah kodmin l'yorshei hashniyah" - and likewise, if both wives died before collecting their kesubah, and their heirs come to collect the kesubah from the heirs. This refers to heirs who are not from this father, that is, they inherit only from their mother and not from their father, and they turn to the heirs who inherited from the father in order to collect their mother's kesubah. The same order applies to them as well: the heirs of the first wife take precedence over the heirs of the second wife.
He married the first and she died, he married a second and then he died:
He married a first wife and she died in his lifetime, and afterward he married a second wife, and then he died and left her a widow. Here two sides stand opposite each other. On one side are the heirs of the first wife, who come to collect their mother's kesubah - what is called kesubas benin dichrin, which we have already dealt with in this tractate. Even though they themselves are heirs to the father's property, they seek to collect the sum of their mother's kesubah before the estate is divided equally among all the sons. On the other side stands the widow, who seeks to collect her own kesubah.
On this the Mishnah decides: "Shniyah v'yorsheha kodmin l'yorshei harishonah" - the second wife who was left a widow, and likewise her heirs if she dies after her husband, take precedence in collecting over the heirs of the first wife.
The reason for the precedence:
The second wife is considered a creditor, like someone holding a note of debt against the estate, and this status applies equally to her and to her heirs. The heirs of the first wife, by contrast, come by virtue of inheritance: even though they are claiming the kesubas benin dichrin, this is nothing other than inheritance, and they themselves are part of the estate. Therefore all claims against the estate must first be cleared away, including the claim of the second wife and her heirs, who are considered creditors, and only after these have been paid do the heirs of the first wife take their inheritance and their kesubas benin dichrin.
A note on the law of the oath:
It is worth noting, and we have already dwelt on this in the past, in a situation where two groups of heirs stand opposite each other: if the second wife, the widow, died after her husband, and her heirs come to collect from the heirs of the first wife, they can collect only if their mother swore the oath required for collecting her kesubah before she died. For if she died without having sworn, her heirs cannot collect the kesubah, because of the rule that a person does not bequeath to his children money that can be collected only by means of an oath. The sons themselves cannot swear and collect; rather, their mother had to swear before her passing.
In summary: we have learned that where a man leaves two wives, the first takes precedence over the second, and her heirs take precedence over the heirs of the second. But where the first wife died in her husband's lifetime and he then married a second wife and died, the second wife and her heirs take precedence over the heirs of the first, because she has the status of a creditor while the heirs of the first come by virtue of inheritance, through the kesubas benin dichrin. And we dwelt on the condition that the heirs' collection depends on their mother having sworn during her lifetime.