Arachin, Chapter 5, Mishnah 5. This chapter continues to examine the language a person uses when he pledges something to the Beit Hamikdash. Our mishnah draws the sharp line between dedicating a particular object and accepting a personal obligation measured by that object's worth, and it shows what happens when the object is lost before the pledge can be carried out.
Dedicating the object itself
Two declarations open the mishnah. In the first, "shor zeh olah": a man points to an ox standing in front of him and consecrates that animal to be offered as an olah. In the second, "bayit zeh korban": he points to his house and declares it hekdesh, so that the building will be sold and the money turned over to the Beit Hamikdash.
Then disaster strikes: "met hashor venafal habayit." The animal perished while still in its owner's possession, never reaching the Mizbe'ach, and the building came down before the treasurer of hekdesh had ever taken hold of it. In such a case the halachah is "eino chayav leshalem": the man who made the declaration is under no financial obligation whatsoever.
The reasoning follows directly from his words. He consecrated this ox and no other, this house and no other. Once that particular ox or that particular house is gone from the world, the dedication has nothing left to attach itself to, and with it the obligation disappears.
Obligating oneself in the object's value
Now the mishnah shifts the formula: "demei shor zeh alai olah." The speaker places an obligation upon himself to bring an olah offering worth as much as this animal is worth. The parallel case is "demei bayit zeh alai korban": he undertakes to deliver to the Beit Hamikdash a sum of money equivalent to what his house is worth.
The same misfortune strikes: "met hashor venafal habayit." The animal perished, the building came down, and no appraisal had yet been carried out. Here, though, the halachah reads "chayav leshalem." The obligation stands. The animal and the building are evaluated in the condition they are in now, after the loss, and he pays that assessment to the Beit Hamikdash. Because he attached the pledge to himself rather than to the property, the debt sits upon him, while the property functions only as the yardstick for measuring what he must give.
Why an animal and a house are not like a person
This calls to mind what we learned earlier: when a person who was pledged in an appraisal dies, no valuation is made at all. Why should an ox or a house be different, and be appraised even after they are lost?
The distinction lies in whether anything of worth remains. The value of a person is measured by the work he can perform, and a corpse can perform none, so nothing is left to assess. But a dead ox is not worthless: its carcass can still be put to use. A house that has caved in is not worthless either: its stones remain and have a price. Whatever those remains are worth at that moment is what the man must appraise, and that sum he is obligated to give to the Beit Hamikdash.