1 Corinthians 8:10
8 Now food will not bring us close to God. We are no worse if we do not eat and no better if we do. 9 But be careful that this liberty of yours does not become a hindrance to the weak. 10 For if someone weak sees you who possess knowledge dining in an idol’s temple, will not his conscience be “strengthened” to eat food offered to idols? 11 So by your knowledge the weak brother or sister, for whom Christ died, is destroyed. 12 If you sin against your brothers or sisters in this way and wound their weak conscience, you sin against Christ. 13 For this reason, if food causes my brother or sister to sin, I will never eat meat again, so that I may not cause one of them to sin.
Avodah Zarah 8aBabylonian Talmud
It is taught in a baraita that Rabbi Yishmael says: Jews who are outside of Eretz Yisrael are considered to engage in idol worship in purity, i.e., unwittingly. How does this occur? In the case of a gentile who prepared a feast for the marriage of his son, and invited all of the Jews in his town, even though they eat of their own kosher food and drink of their own kosher beverages, and their own attendant stands before them, the verse ascribes guilt to them as though they ate of the offerings to the dead, i.e., idols, as it is stated: “And sacrifice to their gods, and they call you, and you eat of their sacrifice” (Exodus 34:15). Since Jews participate in a feast in which the gentile sacrifices offerings to his idol, it is as though they partook of the offering themselves.
Notes and References
"... The logical extension of Paul's conception was that all things are pure to the pure, precisely the formulation attributed to him in Titus 1:15. But Paul's actual practice turned out to be otherwise. In 1 Corinthians he indeed departs from the policy of James by accepting that food offered to idols might be eaten, on the grounds that idols represent entirely fictional gods (1 Corinthians 8:4-6). But he also warns against eating such food if some who believe in such gods are confirmed in their idolatry, so that "their conscience, being weak, is defiled" (1 Corinthians 8:7-13, especially verse 7). The defilement here is internal and moral, rather than pragmatic, but it is nonetheless dangerous; Paul declares that he would rather not eat meat at all than cause a brother to sin (1 Corinthians 8:13: see the restatement of the principle in Romans 14:13-23). Because he is dealing here with matters of pragmatic action, there is no reason to take his statement as metaphorical: he here commends selective fasting for the sake of fellowship. By means of his own, characteristic argument, Paul approximates to what the rabbis would come to teach concerning the danger of idolatrous feasts (see b. Avodah Zarah 8a, instruction in the name of Rabbi Ishmael) ..."
Neusner, Jacob & Chilton, Bruce Classical Christianity and Rabbinic Judaism: Comparing Theologies (p. 147) Baker Academic, 2004