John Gill Commentary Ecclesiastes 8:13

"but it shall not be well with the wicked, neither shall he prolong [his] days, [which are] as a shadow; because he feareth not before God." — Ecclesiastes 8:13 (ASV)

But it shall not be well with the wicked It shall be ill with him; more is designed than is expressed, (Isaiah 3:11); in life they have no solid peace and comfort; at death they will be turned into. At judgment they will hear the awful sentence, "Go, you cursed", and will be in torment to all eternity, (Matthew 25:41);

neither shall he prolong [his] days, [which are] as a shadow : wicked men sometimes do not live out half their days, which, according to the course of nature, and common term of life, they might be thought to live; or if they prolong their days in wickedness, as sometimes they do, (Ecclesiastes 7:15); yet their days at longest are but a shadow which declines, and is quickly gone; or, however, they do not attain to eternal life, which is sometimes meant by prolonging days, and is length of days for ever and ever, (Isaiah 53:10) (Psalms 21:4); this they never enjoy; but when the righteous go into life lasting, they go into everlasting punishment.

The reason of this is, because he feareth not before God ; the fear of God is not before his eyes, nor in his heart; he goes on in sin without fear of him, boldly and openly commits it, and instead of taking shame for it, or repenting of it, glories in it; stretches out his hand against God, and bids defiance to him, and desires not the knowledge of him, and refuses to obey him

The Targum of the whole is,``and it shall not be well with the wicked, and he shall have no space in the world to come; and in this world his days shall be cut off, and they shall flee and pass away as a shadow, because he fears not God.''