From the Mishnah:
There are four traits among those who sit before the sages:
a sponge, a funnel, a strainer, and a sifter.
A sponge—because he sponges everything up;
a funnel—because he takes in on one side and lets out on the other;
a strainer—for he lets out the wine and keeps in the lees;
and a sifter—for he lets out the flour and keeps in the finest flour.
(Avot 5:15)
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