He also that is slothful - A slothful man neglects his work, and the materials go to ruin: the master, he destroys the materials. They are both destroyers.

He also that is slothful in his work,.... Remiss in it; hangs down his hands, and does not care to make use of them, but neglects his business:
is brother to him that is a great waster: a prodigal man, who spends his substance in riotous living: the sluggard and the prodigal are brethren in iniquity; for, though they take different courses, they are both sinful, and issue in the same manner; both bring to poverty and want. Or, "brother to a master that wastes" (p); a slothful servant and a wasteful master are near akin, and come into the same class and circumstances. Jarchi interprets it,
"he that separateth from the law, though a disciple of a wise man, is a brother to Satan;''
whose name is Apollyon, the waster and destroyer. A man that is slothful in spiritual things, though a professor of religion, and has a place in the house of God, is brother to him that is a waster and persecutor of it; see Matthew 12:30.
(p) "domino devaststionis", Gejerus; "domino dissipanti", Mercerus.

Omissions of duty, and in duty, are fatal to the soul, as well as commissions of sin.

One by failing to get, the other by wasting wealth, grows poor.
waster--literally, "master of washing," a prodigal.

9 He also who showeth himself slothful in his business,
Is a brother to him who proceedeth to destroy.
The Hithpa. התרפּה signifies here, as at Proverbs 24:10, to show oneself slack, lazy, negligent. מלאכה is properly a commission for another, as a king has a messenger, ambassador, commissioner to execute it; here, any business, whether an undertaking in commission from another, or a matter one engages in for himself. He who shows himself slack therein, produces in his way, viz., by negligence, destruction, as truly as the בּעל משׁחית, who does it directly by his conduct. Thus one is named, who is called, or who has his own delight in it, to destroy or overthrow. Jerome, incorrectly limiting: sua opera dissipantis. Hitzig well compares Matthew 12:30. In the variation, Proverbs 28:24, the destroyer is called אישׁ משׁחית, the connection of the words being adject.; on the contrary, the connection of בעל משׁחית is genit. (cf. Proverbs 22:24; Proverbs 23:2, etc.), for משׁחית as frequently means that which destroys = destruction. Von Hofmann (Schriftbew. ii. 2, 403) understands 'אישׁ מ of the street robber, 'בעל מ of the captain of robbers; but the designation for the latter must be 'שׂר מ, though at 1-Kings 11:24 he is called by the name שׂר גּדוּד. The form of the word in the proverb here is more original than at 38:24. There חבר [companion] is used, here אח [brother], a general Semitic name of him who, or of that which, is in any way related to another, cf. Job 30:29. Fleischer compares the Arab. proverb: âlshbht âkht alkhṭyât, scepticism is the sister of sin.

Is brother - Though they take several paths, yet both come to one end.