For they cannot sleep unless they have done wrong; they are robbed of sleep unless they have made someone stumble.
Some make David's instructions to Solomon, which began Pro 4:4, to continue to the end of the chapter; nay, some continue them to the end of the ninth chapter; but it is more probable that Solomon begins here again, if not sooner. In these verses, having exhorted us to walk in the paths of wisdom, he cautions us against the path of the wicked. 1.
Commenting on Proverbs 4:14-19
For they sleep not, except they have done mischief,.... Or they cannot sleep, as Jarchi and Gersom interpret it. Oftentimes they cannot sleep on their beds for devising mischief, their thoughts are so intensely set on contriving wicked schemes; and when they have so done, they cannot sleep until they have executed them; they are continually restless and uneasy day and night, like the troubled...
The reason is found in the character of sinners, whose zeal to do evil is forcibly depicted (Pro 6:4; Psa 36:5). They live by flagrant vices (Pro 1:13). Some prefer to render, "Their bread is wickedness, their drink violence" (compare Job 15:16; Job 34:7).