וְרָאִ֨יתִֽי אֲנִ֜י אֶת־כָּל־עָמָ֗ל וְאֵת֙ כָּל־כִּשְׁר֣וֹן הַֽמַּעֲשֶׂ֔ה כִּ֛י הִ֥יא קִנְאַת־אִ֖ישׁ מֵרֵעֵ֑הוּ גַּם־זֶ֥ה הֶ֖בֶל וּרְע֥וּת רֽוּחַ׃
Again, I considered all labour and all excelling in work, that it is a man’s rivalry with his neighbour. This also is vanity and a striving after wind.
Rashi on Ecclesiastes
And I observed that all labor. These are the sins, which are toil in the eyes of the Holy One, Blessed Is He.
Rashi on Ecclesiastes
And all skillful work. Which is not for the sake of Heaven, but for one’s envy of his friend, both of which are vanity.
Rashi on Ecclesiastes
Is the result of man’s envy. Which is the result of man’s envy of his neighbor.