18 I hated all my toil in which I toil under the sun, seeing that I must leave it to the man who will come after me, 19 and who knows whether he will be wise or a fool? Yet he will be master of all for which I toiled and used my wisdom under the sun. This also is vanity. 20 So I turned about and gave my heart up to despair over all the toil of my labors under the sun, 21 because sometimes a person who has toiled with wisdom and knowledge and skill must leave everything to be enjoyed by someone who did not toil for it. This also is vanity and a great evil. 22 What has a man from all the toil and striving of heart with which he toils beneath the sun? 23 For all his days are full of sorrow, and his work is a vexation. Even in the night his heart does not rest. This also is vanity. 24 There is nothing better for a person than that he should eat and drink and find enjoyment in his toil. This also, I saw, is from the hand of God, 25 for apart from him who can eat or who can have enjoyment? 26 For to the one who pleases him God has given wisdom and knowledge and joy, but to the sinner he has given the business of gathering and collecting, only to give to one who pleases God. This also is vanity and a striving after wind.

(Ecclesiastes 2:18-26 ESV)

4 Then I saw that all toil and all skill in work come from a man's envy of his neighbor. This also is vanity and a striving after wind. 5 The fool folds his hands and eats his own flesh. 6 Better is a handful of quietness than two hands full of toil and a striving after wind.

(Ecclesiastes 4:4-6 ESV)

15 As he came from his mother's womb he shall go again, naked as he came, and shall take nothing for his toil that he may carry away in his hand. 16 This also is a grievous evil: just as he came, so shall he go, and what gain is there to him who toils for the wind? 17 Moreover, all his days he eats in darkness in much vexation and sickness and anger. 18 Behold, what I have seen to be good and fitting is to eat and drink and find enjoyment in all the toil with which one toils under the sun the few days of his life that God has given him, for this is his lot. 19 Everyone also to whom God has given wealth and possessions and power to enjoy them, and to accept his lot and rejoice in his toil--this is the gift of God. 20 For he will not much remember the days of his life because God keeps him occupied with joy in his heart.

(Ecclesiastes 5:15-20 ESV)

7 Go, eat your bread with joy, and drink your wine with a merry heart, for God has already approved what you do. 8 Let your garments be always white. Let not oil be lacking on your head. 9 Enjoy life with the wife whom you love, all the days of your vain life that he has given you under the sun, because that is your portion in life and in your toil at which you toil under the sun. 10 Whatever your hand finds to do, do it with your might, for there is no work or thought or knowledge or wisdom in Sheol, to which you are going.

(Ecclesiastes 9:7-10 ESV)