Hevel in Kohelet Another Subversive Sequel?

(17) To Adam God said, “Because you did as your wife said and ate of the tree about which I commanded you, ‘You shall not eat of it,’ Cursed be the ground because of you; By toil shall you eat of it All the days of your life: (18) Thorns and thistles shall it sprout for you. But your food shall be the grasses of the field; (19) By the sweat of your brow Shall you get bread to eat, Until you return to the ground— For from it you were taken. For dust you are, And to dust you shall return.”

(20) Both go to the same place; both came from dust and both return to dust.

(7) And the dust returns to the ground As it was, And the lifebreath returns to God Who bestowed it.

(1) Now the man knew his wife Eve, and she conceived and bore Cain, saying, “I have gained a male child with the help of the LORD.” (2) She then bore his brother Abel. Abel became a keeper of sheep, and Cain became a tiller of the soil. (3) In the course of time, Cain brought an offering to the LORD from the fruit of the soil; (4) and Abel, for his part, brought the choicest of the firstlings of his flock. The LORD paid heed to Abel and his offering, (5) but to Cain and his offering He paid no heed. Cain was much distressed and his face fell. (6) And the LORD said to Cain, “Why are you distressed, And why is your face fallen? (7) Surely, if you do right, There is uplift. But if you do not do right Sin couches at the door; Its urge is toward you, Yet you can be its master.” (8) Cain said to his brother Abel … and when they were in the field, Cain set upon his brother Abel and killed him. (9) The LORD said to Cain, “Where is your brother Abel?” And he said, “I do not know. Am I my brother’s keeper?” (10) Then He said, “What have you done? Hark, your brother’s blood cries out to Me from the ground! (11) Therefore, you shall be more cursed than the ground, which opened its mouth to receive your brother’s blood from your hand. (12) If you till the soil, it shall no longer yield its strength to you. You shall become a ceaseless wanderer on earth.” (13) Cain said to the LORD, “My punishment is too great to bear! (14) Since You have banished me this day from the soil, and I must avoid Your presence and become a restless wanderer on earth—anyone who meets me may kill me!” (15) The LORD said to him, “I promise, if anyone kills Cain, sevenfold vengeance shall be taken on him.” And the LORD put a mark on Cain, lest anyone who met him should kill him. (16) Cain left the presence of the LORD and settled in the land of Nod, east of Eden.

(4) I have also noted that all labor and skillful enterprise come from men’s envy of each other—another futility and pursuit of wind!

(3) If a man begot a hundred children and lived many years, and many were the days of his life, he might yet not be sated with good things, and even a burial he might not have. I said: better than he is the stillborn.

(Robert Alter's translation)

All existence on earth was blotted out—man, cattle, creeping things, and birds of the sky; they were blotted out from the earth. Only Noah was left, and those with him in the ark.

"Even if a man should beget a hundred children" (Kohelet 6:3) - this refers to Cain, who had one hundred children. "And live many years" - he lived many years...

Rabbi Shmuel said: "all existence" [ye'kum] (Bereishit 7:23) - this refers to Cain, who drowned. "Better than he is the stillborn" (Kohelet 6:3) - this refers to Abel his brother...