A judge is not allowed to accept a gift from any party in a lawsuit, even if they’re asking him to do the right thing; this is derived from the repetition of this mitzvah in parshas Shoftim. (What does the repetition add to our knowledge of the mitzvah? That we may not even accept a pay-off to render a true verdict.) Our verse continues that bribes blind even the most honest of people. It’s impossible to remain impartial after accepting a gift from one of the parties.
One who offers a bribe violates the prohibition against metaphorically placing a stumbling block before a person, as we shall see in Mitzvah #232. The Rambam rules that one who has accepted a bribe is required to return it (see Hilchos Sanhedrin 23:1). A judge is, however, allowed to charge for his services, but it must be a set fee paid by both parties equally.
Any type of gift or favor is considered bribery, even flattery. The Talmud in Kesubos (105b) relates a number of incidents in which judges recused themselves because of some common courtesy extended them by one party or the other. In one instance, Rabbi Yishmael b. R. Yosi had a sharecropper who would deliver a basket of produce from his orchard each week on Friday. On one occasion, he brought it on Thursday, saying that he had to see Rabbi Yishmael for a court case anyway. Even though it was his own property, bringing it early constituted a favor and therefore, however unintentionally, a bribe. Rabbi Yishmael refused to take the produce early and recused himself from hearing the case. He did, however, sit in on the case to see how it went. He discovered that, throughout the hearing, he found himself thinking how the sharecropper should plead in order to win the case. Having observed how even an abortive attempt to deliver his own property colored his judgment, Rabbi Yishmael declared, “Cursed be those who accept bribes! I didn’t even accept my own property and it still biased my judgment. How much more must those who actually accept bribes be biased!”
This mitzvah is in effect in all times and places for the members of a beis din. In the Talmud, it can be found in the tractate of Kesubos (105a-b). In the Shulchan Aruch, it is codified in Choshen Mishpat 9. (The section emphatically begins with the words “meod meod” – a judge must be very, very careful to avoid the possibility of a bribe.) It is #274 of the 365 negative mitzvos in the Rambam’s Sefer HaMitzvos and #71 of the 194 negative mitzvos that can be fulfilled today as listed in the Chofetz Chaim’s Sefer HaMitzvos HaKatzar.