לְבַד֙ רְאֵה־זֶ֣ה מָצָ֔אתִי אֲשֶׁ֨ר עָשָׂ֧ה הָאֱלֹהִ֛ים אֶת־הָאָדָ֖ם יָשָׁ֑ר וְהֵ֥מָּה בִקְשׁ֖וּ חִשְּׁבֹנ֥וֹת רַבִּֽים׃
Behold, this only have I found, that God made man upright; but they have sought out many inventions.
Read kabbalistic (mystical) interpretation of Ecclesiastes 7:29: and classical mystical sources.