Ecclesiastes 4:4; Ecclesiastes 4:7-8

4 Again, I considered all travail and every right work for which a man is envied by his neighbor. This is also vanity and vexation of spirit.

7 Again I returned, and I saw vanity under the sun:

8 There is one who is alone, and there is not a second; yea, he hath neither child nor brother, yet there is no end to all his labor. Neither is his eye satisfied with riches; nor saith he, "For whom do I labor and bereave my soul of good?" This is also vanity; yea, it is a sore travail.