Yahweh, via Hosea, had this main complaint against the northern Israelites that they kept on adoring these idol Baal images. They kept on sinning. They made their own silver idols. They made their own images without any understanding, clearly the work of artisans. When they were finished, they wanted the people to sacrifice to these idols. They wanted people to kiss these idol calves. Yahweh was going to punish them. They were going to become like the morning mist that disappears during the day. They were going to be like chaff that blows in the wind from the threshing floor. They were going to be like smoke from a window. They would disappear before their very own eyes.
Death is the final stage of man. Qoheleth says that we know the human condition. Humans do not dispute with stronger humans. They use words. How can one be better with just words since they are useless and vain? Who even knows what is good for mortals. Then in his usual despairing attitude, Qoheleth maintains that our few days on earth are just passing away like shadows, here today and gone tomorrow. If there is no sunshine, there is no shadow. Darkness comes and the shadow disappears. Who can tell what is going to happen after you have left your place in the sun and your shadows?