And it would follow a fortiori, viz.: If his money requires three, how much more so, his body! It is, therefore, written (re plague-spots, Vayikra 13:3) "… or to one of his sons, the Cohanim" — One Cohein rules on a plague-spot.
(Devarim 21:6) "And all the elders of that city": Even if they are a hundred. Because we said above ([21:2] re the measuring), three or five, I might think that this is so here, too. (in respect to the washing of the hands); it is, therefore, written "and all the judges of that city" — even if they are a hundred.