Chapter 7, Mishnah 1. Before we turn to the Mishnah itself, we need to review the difference between the two types of property a wife brings with her into the marriage.
Two types of property a wife brings into the marriage:
Nichsei melog - property that remains in the wife's ownership, while the husband is entitled to enjoy only its produce. Take an orchard, for example: the husband takes the fruit and all the benefit it yields, but the principal remains hers, and if they are divorced or she is widowed, she receives this property back.
Nichsei tzon barzel - the property is appraised, and the husband writes in the kesubah that he assumes responsibility for it, so that if they are divorced or she is widowed he pays her its value. The property itself becomes his, since he has undertaken to pay for it.
It emerges that nichsei melog do not belong to the husband but to the wife, and he merely derives benefit from them, whereas nichsei tzon barzel belong to the husband.
Our Mishnah deals with slaves - whether melog slaves or tzon barzel slaves - and how the question of ownership affects their ability to eat Terumah when the husband is a kohen.
The ruling of the Mishnah:
A widow who married a Kohen Gadol, which is a forbidden union, and likewise a divorcee or a chalutzah who married an ordinary kohen, which is also a forbidden union, and she brought in melog slaves that belong to her or tzon barzel slaves that belong to him - the ruling depends on the question of ownership:
Melog slaves - they do not eat Terumah. For she herself cannot eat Terumah, having become a chalalah through this relationship; and since the slaves belong to her and she is a chalalah, she has no power to feed them. Slaves do not eat when their owner does not eat.
Tzon barzel slaves - they do eat Terumah. They belong not to her but to the husband, and the husband, even though he is in a forbidden relationship and is not permitted as a kohen or as a Kohen Gadol to be married to this woman, is nevertheless a valid kohen and is not a chalal. Therefore his slaves eat Terumah, since their master the kohen eats Terumah.
"V'eilu hen avdei melog":
What defines melog slaves, which belong to the wife? "Im meisu, meisu lah" - if they died, the loss is hers, since they belong to her. "Hosiru, hosiru lah" - if they increased in value, the gain is hers, for they are hers. "Af al pi shechayav bimzonosan" - even though the husband is obligated in their support, because he derives benefit from them throughout the years of the marriage, "harei eilu lo yochlu bitrumah". The reason, as explained, is that in terms of ownership they are the wife's property, and since she is in a forbidden relationship and is a chalalah who does not eat Terumah, they too do not eat Terumah.
"V'eilu hen avdei tzon barzel":
"Im meisu, meisu lo" - if they died, the loss is his, and he must still pay her the sum of money he undertook for them in the kesubah. "Hosiru, hosiru lo" - if they increased in value, the profit is his. "Ho'il v'hu chayav b'achrayusan" - since the responsibility is his and he must pay for them in any event, "harei eilu yochlu bitrumah". That is, they are his, and therefore they eat Terumah, since their owner is a kohen who eats Terumah.
In summary: in this Mishnah we learned that whether slaves may eat Terumah is determined by who owns them. In the case of a widow married to a Kohen Gadol, or a divorcee or chalutzah married to an ordinary kohen, the wife becomes a chalalah and does not eat Terumah, and therefore melog slaves, which belong to her, do not eat Terumah - even though the husband is obligated in their support. Tzon barzel slaves, by contrast, for which the husband bears responsibility and which belong to him, do eat Terumah, since the husband is a valid kohen and not a chalal.