Mishnayos Avos Perek 5 Mishnah 15

Among those who sit before the sages: Earlier with the "four temperaments among students," it was speaking about the topic of memory and forgetting. And now it is speaking about the topic of proper analysis and separating a thing that is right from that which is not right.

the sponge: It absorbs the water, whether it is muddy or clear. So [too], there is one whose heart is broad and he receives everything that he hears [but] does not have the ability to separate the truth from the falsehood.

the funnel: A vessel that is put at the opening of a barrel or at the opening of a pouch when one wants to fill it with wine or oil.

because it lets in at [one end] and lets out at [the other]: So [too], there is one who receives everything that he learns; [but] in the way that he absorbs it, so does he [relinquish] it.

The strainer: He lets out all that he has heard in the House of Study and collects a wasteful matter.

The sieve: After we take out the bran and the bruised grain from the ground flour, the [inferior powdery] flour is left with the coarse fine flour, and [the latter] is the [more] important one; we pass it through a very fine sieve. And all of the [powdery] flour - which is like white dust - falls from it, and the coarse important flour remains. And so would they do with grain offerings. So [too], there is one who has the ability to separate and to cleanse his teachings and take the truth from the false and wasteful.