One who digs a pit may ¹  fall into it, and one who breaks through a wall may be bitten by a snake. ² 

I have observed the burden that God has given to people ¹  to keep them occupied.

For a man may do his work with wisdom, knowledge, and skill; however, he must hand over ¹  the fruit of his labor ²  as an inheritance ³  to someone else who did not work for it. This also is futile, and an awful injustice! ⁴ 

I decided ¹  to carefully ²  and thoroughly examine ³  all that has been accomplished on earth. ⁴  I concluded: ⁵  God has given people ⁶  a burdensome task ⁷  that keeps them ⁸  occupied. ⁹ 

There is no end to all the people ¹  nor to the past generations, ²  yet future generations ³  will not rejoice in him. This also is profitless and like ⁴  chasing the wind.