Avodah Zarah, Chapter 4, Mishnah 2. The Mishnah continues to discuss items found around the idolatry of Markulis, but that is not its main subject. The main subject of the Mishnah is to clarify the status of two categories of items: things that serve to beautify and adorn the idolatry, which are considered its accessories and are forbidden to derive benefit from; and things that are an offering, sacrifices brought to the idolatry, which are likewise forbidden to derive benefit from when they meet the Mishnah's conditions.
The form of the Markulis in our Mishnah:
The idolatry that the Mishnah deals with is Markulis, but not as it was pictured in the previous Mishnah. There it was described as a heap of stones, as it was in earlier eras. As the generations progressed things became more sophisticated, in quotation marks, and the Markulis was designed not as a heap of stones but as a single rectangular pillar with a carved head on top. Stones were still placed behind it or at its side, but the structure itself became far more elaborate. In English these statues are called a herm, after Hermes, the Greek version of that same idolatry - Mercury, Markulis. This is the Markulis that the Mishnah here has in mind.
"Matza b'rosho ma'os":
One who finds on the head of the idolatry of Markulis coins, or a garment, or vessels - "harei eilu mutarim" - these are permitted, and one may derive benefit from them. The reason is that these items are placed in a manner that does not serve to adorn the idolatry, to glorify it or improve its appearance; in other words, they do not serve it. On the contrary, they were left there in a manner that indicates disgrace toward it, since folded clothing lies on its head as though it were nothing more than a rack and not an idolatry of any importance.
Coins - when they are placed in a pouch hanging around its neck, which is degrading, a sort of graffiti if you will.
A garment - clothing laid on its head not for the sake of adornment.
Vessels - such as a bucket placed upside down on the head of the idolatry, which is no adornment at all.
By contrast, if the adornment were genuinely intended to beautify it - such as a crown on its head or a chain around its neck - it would be forbidden to derive benefit from it as an accessory of idolatry.
Offerings to idolatry:
The Mishnah continues: "parchilei anavim v'atarot shel shibolim v'yeinot ushmanim usolatot v'chol davar shekayotzei bo karev al gabei hamizbe'ach - asur" - clusters of grapes, wreaths of grain (like the wreaths that were placed on the head of the victor in the ancient Greek Olympics), or wine, oil and fine flour in jugs placed beside the idolatry. All of these are considered an offering and are forbidden to derive benefit from.
The Mishnah identifies very specific items here, because they are the sort of things that we offer to Hashem on the altar: items that are sacrificed, fruits brought as bikkurim, flowers used in meal offerings, oil poured over the sacrifice and wine poured as a libation. Similarly forbidden would be items such as logs of wood and even salt, which are also offered to Hashem.
Two criteria in defining a forbidden offering:
That the item is of the sort brought to Hashem, as our Mishnah explicitly identifies.
That the item is brought in the manner in which we bring offerings to Hashem. The Gemara gives an example: even one who takes a branch and breaks it for the sake of the idolatry, this parallels the slaughtering of an animal. So too items that are slaughtered, poured out as a libation, or items of incense offered by burning - all of these are forbidden as an offering, even though they are not of the sort that are offered to Hashem on the altar, since they were brought in this manner.
Either one of these two categories is enough to render it forbidden.
The difference in the law of nullification:
A major difference between the two types, as we will see more fully in the coming mishnayos, emerges in the laws of nullification, that is, the removal of the sanctity. It is possible to nullify the accessories of an idol and its decorative elements and thereby remove them from use: the string of beads around the idol is forbidden, but if the string breaks or the idol breaks, the string becomes permitted. An offering brought to an idol, by contrast, remains forbidden forever, even if the idol is nullified and taken out of use.
In summary: In this mishnah we learned to distinguish between items placed on an idol not for decorative purposes - money, clothing and vessels - which are permitted for benefit, and genuine ornaments, which are forbidden as accessories; and we learned the definition of a forbidden offering by two criteria: something of the type that is offered to Hashem, or something offered in the manner in which offerings are brought to Hashem. We also noted the fundamental difference between them with regard to nullification - accessories and ornaments can be nullified, whereas an offering is forbidden forever.