Mishnah — Seder Nezikin, Tractate SanhedrinChapter 3…
“ Rabbi Meir explains that each litigant can choose a judge and together they choose a third. The sages, however, state that the third judge is chosen by the other two. After this, a process of invalidation (voir dire) is explained, without an explanation of what makes a judge or witness "otherwise forbidden," which is explained later in this chapter. ”
