The prohibition against Avoda Zara is the most severe prohibition in the Torah. It includes the belief and worship of all deities whether on their own or in concert with God, whether they are perceived as spiritual, natural forces or animals. Any worship of these deities, whether worshiping the concept, the thing itself or a representative object, is forbidden as Avoda Zara. This prohibition appears in the Ten Commandments and is repeated throughout the Torah and the books of the prophets. In explanation of the severity of this act it must be understood that idol worship is the antithesis of the most basic Jewish concept, that is, the belief in a single, unique God who rules over all things. The Rabbinic statement that expresses this idea states “Whoever accepts Avoda Zara denies the entire Torah.”
Due to the severity of this prohibition, we find that the Torah commands us not only to refrain from idol worship, but also to destroy it and to stay away from it and from its adherents in a variety of different ways. Thus we are forbidden from following the ways of idol worshipers or attempting to appear like them (see, for example, Vayikra 18:3). The Sages added further limitations whose purpose is to discourage interaction with Avoda Zara and its followers.
Massekhet Avoda Zara is found in Seder Nezikin as one of the tractates that follows Massekhet Sanhedrin, and it expands on the ideas that are found there. While Massekhet Sanhedrin focuses on the criminal aspects of Avoda Zara, the punishments for its worship, and so on, Massekhet Avoda Zara deals with what is permissible and what is forbidden, under what circumstances, etc.
Another interesting aspect of Avoda Zara that is discussed in Massekhet Sanhedrin is the fact that Avoda Zara is forbidden not only to Jews but to all people of the world, as it is one of the Seven Noaḥide laws. This impacts on Jews, as well, since they are commanded to destroy the idol worship in the land of Israel and, theoretically, throughout the world. Even if is not within the power of the Jewish people to accomplish this, nevertheless Jews are not allow to support those who want to worship idols or assist them in doing so.
As noted, the focus of Massekhet Avoda Zara is on the need to remove oneself from idol worship and things connected with it. It is forbidden to derive benefit from the idols themselves, as well as their ornaments and donations made to them, and the Sages even decreed a severe level of ritual defilement for coming in contact with them. Similarly, participating in pagan holidays and festivals is forbidden. Much of Massekhet Avoda Zara works at defining the boundaries of what would be forbidden, whether indirect benefit from Avoda Zara or passive participation in religious ceremonies would be permitted.
Part of the prohibition against benefitting from Avoda Zara forbids eating food that has been sacrificed as part of a pagan ritual. One aspect of these laws revolves around wine, and specifically yayin nesekh – wine that was libated on an altar to a deity. It was common practice for idol worshipers to pour off a small amount of wine to honor their deity before drinking. Such a libation would prohibit the wine, and the practice was so widespread that it was reasonable to assume that any wine that had been touched by a non-Jew had likely been poured off to a pagan deity. This led to the establishment of a Rabbinic injunction of stam yeinam – that even ordinary wine of non-Jews that had not been used for religious purposes was forbidden. This ruling was made both because of the concern with yayin nesekh as well as because of a general interest in limiting the social interaction between Jews and pagans, as the Gemara teaches (Massekhet Avoda Zara 36b) “The Sages decreed about their wine because of their daughters.”
Since Massekhet Avoda Zara teaches about the need to remove oneself from idol worship and associated practices, it is necessary to describe the details of some of the common activities that were done as Avoda Zara. What we find in this tractate are mainly descriptions of Greco-Roman pagan practices as they expressed themselves in Israel and surrounding countries during the period of the Talmud. The Talmud anticipates that we will be able to reach conclusions regarding other pagan practices based on what we find here.
The teachings of the Torah focus on actual Avoda Zara, and into the times of the Mishna and Gemara Jews found themselves living among people who practiced pagan religions. Over time, however, new religions developed whose basis is in Jewish belief – such as Christianity and Islam – which are based on belief in the Creator and whose adherents follow commandments that are similar to some Torah laws (see the uncensored Rambam in his Mishne Torah, Hilkhot Melakhim 11:4). All of the rishonim agree that adherents of these religions are not idol worshippers and should not be treated as the pagans described in the Torah. Moslems certainly worship a single God and do not offer libations of wine. There are different approaches to Christians, where we find that the Rambam views them as basically pagans, while Tosafot – and even more so the Meiri – view them as monotheists. Therefore, although many of the laws limiting interaction with non-Jews remain in place in order to avoid intermarriage and assimilation, other laws – e.g. limits on business dealings prior to their holidays – are assumed to be permitted. This is based on statements made in the Gemara that in the Diaspora it is impossible for Jews to avoid such interactions (7b) and that non-Jews living in Diaspora countries are not truly idol worshippers, they are just following the traditions of their fathers (Massekhet Ḥullin 13b).