Halakhah sur Les Nombres 27:23

And we never set up a sanhedrin - whether big or small - except [with] ordained judges. And Moshe, our teacher, ordained Yehoshua, his student, with his hands (by pressing his hands upon him), as it is written (Numbers 27:23), "He pressed his hands upon him." And likewise, he ordained the seventy elders that he gathered to himself; and those elders ordained others, and others, others, until the end of all those ordained. However the ordination of all the generations was not with the hand, like the ordination of Moshe; but rather they would check if the one they wanted to ordain was an expert in the wisdom of the Torah and if he was healthy and complete in his intellect and if was a man that loves truth and hates wrongdoing and all of its content. And after great investigation into his makeup and his wisdom, three ordained sages - or even if only one of them was ordained - would say to him, "Behold, you are ordained." And from that time, they call him, "rabbi," and he has permission afterwards to even adjudicate cases of penalties. And the law that a judge [who is] very old, a eunuch, blind even in one of his eyes or does not have children is not fit to be on a sanhedrin; the law that the kings of the House of David judge and we judge them, but not the [other] kings of Israel, since they are not assumed to be fit like [the House of David]; the law [about] until when the Great Sanhedrin or a small one or a court of three sit [in judgement]; and the rest of its details are [all] elucidated in Tractate Sanhedrin.