As it absorbs, so it emits/ light come light go/ in at one ear, out at the other/to learn quickly and forget as soon
In the question: He who understands and receives quickly is also quick to forget. "He who hears quickly is quick to lose" (in the source: the meaning of a vessel made of a material capable of receiving and releasing food substances from its contents, a discussion of the meaning of hearing in the laws of kosher)
(“As it absorbs, so it emits; what it absorbed in sparks, it also emits in sparks” - Avodah Zarah 76b)
Translation
Expression (Hebrew)
כְּבוֹלְעוֹ כָּךְ פּוֹלְטוֹ
Definition (Hebrew)
בְּהַשְׁאָלָה: מֵבִין וְקוֹלֵט מַהֵר אַךְ מְמַהֵר לִשְׁכֹּחַ. "מַהֵר לִשְׁמֹעַ וּמַהֵר לְאַבֵּד" (בַּמָּקוֹר: הַכַּוָּנָה לְסוּג כְּלִי הֶעָשׂוּי מֵחֹמֶר הַיָּכוֹל לְקַבֵּל וְלִפְלֹט מִתּוֹכוֹ חָמְרֵי מָזוֹן, דָּבָר בַּעַל מַשְׁמָעוּת בְּדִינֵי כַּשְׁרוּת)
("כְּבוֹלְעוֹ כָּךְ פּוֹלְטוֹ, מָה בֻּלְּעוּ בִּנְצוּצוֹת, אַף פּוֹלְטוֹ בִּנְצוּצוֹת"- עֲבוֹדָה זָרָה עו ע"ב)