כִּ֣י אִם־שָׁנִ֥ים הַרְבֵּ֛ה יִחְיֶ֥ה הָאָדָ֖ם בְּכֻלָּ֣ם יִשְׂמָ֑ח וְיִזְכֹּר֙ אֶת־יְמֵ֣י הַחֹ֔שֶׁךְ כִּֽי־הַרְבֵּ֥ה יִהְי֖וּ כָּל־שֶׁבָּ֥א הָֽבֶל׃
For if a man live many years, Let him rejoice in them all, And remember the days of darkness, For they shall be many. All that cometh is vanity.
Read midrashic interpretation of Ecclesiastes 11:8: and classical rabbinic exegesis.