Many Old Camels Are Marked in the Hides of Young Calves/ many young men die before the old
By metaphor: young age does not guarantee longevity (see also: "Many travelers died and their hides were spread flat on the backs of their camels").
("Nadab said to his father: My father, when the two old men had died, and you and I would lead the generation? The Holy One, blessed be He, said to him: Let us see who will bury me. Rav Papa said: These are the words of my people: my soul, my grandfather's camels, my grain, my donkey's bedding" - Sanhedrin Nov. 1)
Translation
Expression (Hebrew)
הַרְבֵּה גְּמַלִּים זְקֵנִים טְעוּנִים בְּעוֹרוֹת בְּכָרִים/בְּכָרוֹת?
Definition (Hebrew)
בְּהַשְׁאָלָה: גִּיל צָעִיר אֵינוֹ מַבְטִיחַ אֲרִיכוּת יָמִים (רְאֵה גַּם:"הַרְבֵּה סְיָחִים מֵתוּ וְנַעֲשׂוּ עוֹרוֹתֵיהֶם שְׁטִיחִים עַל גַּבֵּי אִמּוּתֵיהֶן").
("אָמַר לוֹ נָדָב לַאֲבִיהוּא: אֵימָתַי יָמוּתוּ שְׁנֵי זְקֵנִים הַלָּלוּ וַאֲנִי וְאַתָּה נַנְהִיג אֶת הַדּוֹר? אָמַר לָהֶן הַקָּדוֹשׁ בָּרוּךְ הוּא: הֲנִרְאֶה מִי קוֹבֵר אֶת מִי. אָמַר רַב פַּפָּא: הָיִינוּ דְּאָמְרֵי אִינָשֵׁי: נְפִישֵׁי גַּמְלֵי סָבֵי דִּטְעִינִי מַשְׁכֵי דְהוּגְנֵי"- סַנְהֶדְרִין נֹב ע"א)