Perek “Rabbi Yishma’el,” the fourth chapter of Masechet Avodah Zarah, begins on today’s daf (=page), and it continues the discussions of the last chapter, whose focus was on defining what might be considered to be forbidden Avodah Zarah. For example, the first discussion in this perek is about the deity Markolis – the Roman god Mercurius, or Mercury – whose representation was not a formal statue in a house of worship, but was a simple pile of rocks built up out in the open air. In this case, even thought there was no statue, nevertheless, the recognizable pile of rocks represented the deity. Even the method of worship was out of the ordinary, inasmuch as travelers would throw rocks on the pile, and they would become part-and-parcel of the idolatrous representation themselves.
The discussion about this deity and its unique method of worship serves as a basis for the basic questions – what is considered to be avodah zarah and what is viewed as a contribution or donation to avodah zarah that becomes forbidden.
The Roman god Mercurius parallels the Greek god Hermes, although some suggest that the deity referred to in the Mishnah was Mercurius Helipolitanus, which was a local Syrian idol, influenced by Greek and Roman traditions.
This deity was viewed by its worshippers as the protector of travelers generally, and of traveling merchants, specifically, which is why the representation of the deity appeared most often at crossroads. Oftentimes, the idol was not a full statue, but was just its head on a base. Worship consisted of throwing a stone or pebble at the statue, and over time a pile of rocks was formed that served as the deity, itself. From the Mishnah it appears that sometimes there was no idol at all, and the representation was simply a symbolic pile of stones – two stones side-by-side with a third stone placed on them.