Ruth 4:2

And he took ten men of the elders of the city
Who were such, not merely in age but in office, who were the heads of thousands, fifties, and tens; ten of whom were a quorum to do business in judiciary affairs, to determine such matters as Boaz had propose, as to whom the right of redemption of a brother and kinsman's widow, and her estate, belonged, and who were the proper witnesses of the refusal of the one to do it, and of the other's doing it and from hence the Jews

and said, sit down here, and they sat down;
and so made a full court.

F5 Misnah Megillah, c. 4. sect. 3. T. Bab. Cetubot, fol. 7. 1. Midrash Ruth, fol. 35. 1.