John Gill Commentary Proverbs 21:5

"The thoughts of the diligent [tend] only to plenteousness; But every one that is hasty [hasteth] only to want." — Proverbs 21:5 (ASV)

The thoughts of the diligent [tend] only to plenteousness
A man that is thoughtful and studious, and wisely forms schemes in his mind, and diligently pursues them; the issue of it is, generally speaking, prosperity and plenty: such a man is usually thriving and flourishing; and this holds good in things spiritual, as well as in things temporal, (Matthew 25:29) ;

but of everyone [that is] hasty only to want ;
that is in haste to be rich, and is resolved to be so, right or wrong, he comes at last to poverty and want: or he who is rash and precipitate in acting, who never thinks before he acts, but rashly engages in an affair; or, however, does not give himself time enough to think it over, but, as soon as ever it has entered his thoughts, he immediately attempts to put it in execution; a man so thoughtless and inconsiderate, so rash and hasty, brings himself and family to poverty; see (Proverbs 20:21) .