Talmud for Pirkei Avot 4:20
אֱלִישָׁע בֶּן אֲבוּיָה אוֹמֵר, הַלּוֹמֵד יֶלֶד לְמַה הוּא דוֹמֶה, לִדְיוֹ כְתוּבָה עַל נְיָר חָדָשׁ. וְהַלּוֹמֵד זָקֵן לְמַה הוּא דוֹמֶה, לִדְיוֹ כְתוּבָה עַל נְיָר מָחוּק. רַבִּי יוֹסֵי בַר יְהוּדָה אִישׁ כְּפַר הַבַּבְלִי אוֹמֵר, הַלּוֹמֵד מִן הַקְּטַנִּים לְמַה הוּא דוֹמֶה, לְאֹכֵל עֲנָבִים קֵהוֹת וְשׁוֹתֶה יַיִן מִגִּתּוֹ. וְהַלּוֹמֵד מִן הַזְּקֵנִים לְמַה הוּא דוֹמֶה, לְאֹכֵל עֲנָבִים בְּשֵׁלוֹת וְשׁוֹתֶה יַיִן יָשָׁן. רַבִּי אוֹמֵר, אַל תִּסְתַּכֵּל בַּקַּנְקַן, אֶלָּא בְמַה שֶּׁיֶּשׁ בּוֹ. יֵשׁ קַנְקַן חָדָשׁ מָלֵא יָשָׁן, וְיָשָׁן שֶׁאֲפִלּוּ חָדָשׁ אֵין בּוֹ:
One who learns as a child, to what can he be compared? To ink written on new paper, [which endures. So, the learning of childhood is not forgotten], and one who learns in old age, to what can he be compared? To ink written on smudged paper. R. Yossi beRabbi Yehudah Ish Kfar Habavli says: One who learns from the young, to what can he be compared? To one who eats dull grapes [i.e., grapes which are unripe and which dull the teeth. (Analogously, the wisdom of a child has not sufficiently matured and his words do not "sit well" on the heart)], and to one who drinks wine from his vat, [which is intermixed with lees. (Analogously, the wisdom of a child is intermixed with doubts.)] And one who learns from the old, to what can he be compared? To one who eats ripe grapes and drinks old wine. Rabbi says: Do not look at the vessel, but at what it contains. There is a new vessel full of old wine, and an old vessel which does not contain even new wine! [Rabbi disagrees with R. Yossi beRabbi Yehudah, saying that just as there is a new vessel full of old wine, so there can be a child whose "flavor" is like that of the old; and there are old men inferior in wisdom to children.]
Jerusalem Talmud Sanhedrin
Avot D'Rabbi Natan
He would also say: Anyone who has studied Midrash but has not studied Halakhah is like a strong person who is unarmed. Anyone who has studied Halakhah but has not studied Midrash is like a weak person with a weapon in his hand. Anyone who has studied both is like a person who is both strong and armed.
He would also say: Be careful when greeting other people. Do not get in the middle of a conflict, and do not try to see it. Return to a place of friends. And be a tail to lions rather than a head to foxes.