Ecclesiastes (Kohelet)
Ecclesiastes 4:2-3
Kohelet praises the dead over the living, and even more so the one who has never been born at all, who has not seen the evil deeds done under the sun.
וְשַׁבֵּ֧חַ אֲנִ֛י אֶת־הַמֵּתִ֖ים שֶׁכְּבָ֣ר מֵ֑תוּ מִן־הַ֣חַיִּ֔ים אֲשֶׁ֛ר הֵ֥מָּה חַיִּ֖ים עֲדֶֽנָה׃ וְטוֹב֙ מִשְּׁנֵיהֶ֔ם אֵ֥ת אֲשֶׁר־עֲדֶ֖ן לֹ֣א הָיָ֑ה אֲשֶׁ֤ר לֹֽא־רָאָה֙ אֶת־הַמַּעֲשֶׂ֣ה הָרָ֔ע אֲשֶׁ֥ר נַעֲשָׂ֖ה תַּ֥חַת הַשָּֽׁמֶשׁ׃
Then I accounted those who died long since more fortunate than those who are still living; and happier than either are those who have not yet come into being and have never witnessed the miseries that go on under the sun.
Why it matters — This is the biblical source that underlies the pessimistic position, and likely the prooftext for the view that it would have been better for man not to have been created.