Tosefta sur Les Psaumes 1:1

The rule is the same for idolators and for Samaritans. One may entrust to them shorn fields, harvested grain, and cut trees. Rabbi Yehuda says, low growth for shearing on the condition that he will shear it, grain to harvest on condition that he will harvest it, trees for cutting on the condition of cutting them. He who visits gentile camps (s’rat’ya’ot), it is prohibited, because of idolatry according to Rabbi Meir, but the Sages say, in a time when they are [actually] making offerings to idols it is prohibited because of idolatry but if they are not making offerings to idols it is prohibited because of “a session of scorners” (Ps 1:1). The one who goes theater and sees the snakes and the members of the muleteers in the saeculares, the saeculare is prohibited because of “a session of scorners” as it says, “And in a session of scorners he did not sit” (Ps 1:1), you learn that these bring a man to neglect studying Torah. The one who visits the theater of the idolators, if he cries out because someone is in need, he is permitted, but if he does it in alliance [with the Romans] it is prohibited. The one who sits in the theater, this is one who sheds blood. Rabbi Natan permits because of two things: because of crying and saving a life and testifying for a woman that would remarry. One may go to the theater in order to cry out and save the life or a camp of besiegers because of the welfare of the town, but if he is counted among them, it is forbidden.