A little sleep, a little slumber, a little folding of the hands to rest - and poverty will come on you like a thief and scarcity like an armed man.
This is not an actual warning against rest and sleep, but against laziness. (There are plenty of Bible verses that speaking of rest, and ultimately finding our rest in Jesus.) Like drifting off for a minute can lead to hours of sleep, falling into laziness can lead to a pattern of laziness. Then you wake up surprised that you have insufficient income to meet your basic needs.