In contrast with the two besetting sins of Eastern monarchs stands their one great duty, to give help to those who had no other helper.
Such as are appointed to destruction - literally, "children of bereavement," with the sense, either, as in the text, of those "destined to be bereaved of life or goods," or of "bereaved or fatherless children."

Open thy mouth for the dumb - For such accused persons as have no counsellors, and cannot plead for themselves.
Are appointed to destruction - בני חלוף beney chaloph, variously translated, children of passage - indigent travelers; children of desolation - those who have no possessions, or orphans. I believe it either signifies those who are strangers, and are travelling from place to place, or those who are ready to perish in consequence of want or oppression.

Open thy mouth for the (g) dumb in the cause of all such as are appointed to destruction.
(g) Defend their cause that are not able to help themselves.

Open thy mouth for the dumb,.... Not who are naturally so, but who cannot speak in their own behalf, either through want of elocution, or knowledge of the laws; or who are bashful, timorous, and fearful, being overawed by the majesty of a court of judicature, or by their prosecutors; or who, as they have not a tongue, so not a purse, to speak for them, the fatherless and the widow; which latter has her name, in the Hebrew language, from dumbness. Here Lemuel's mother advises him to open his mouth freely, readily, boldly, and intrepidly, and plead for such persons. Even
in the cause of all such as are appointed to destruction; whose destruction is resolved on by their accusers and prosecutors; and who are in danger of it, being charged with capital crimes; unless some persons of wisdom, power, and authority, interpose on their behalf. It may be rendered, "in the cause of all the children of change", or "passing away" (s); the children of the world, which passeth away with all things in it, as Kimchi; or orphans, whose help passeth away, as Jarchi; or rather strangers, as others, who pass from place to place and whose state and condition is liable to many changes who may be ignorant of the laws of the country where they are, and may stand in need of persons to plead for them.
(s) "filiormn transitus", Montanus, Gejerus, Michaelis; "transeuntis, sub. seculi", Vatablus, so Ben Melech; "filiorum mutationis loci", Piscator; "filii mutationis, h. e. hujus mundi", Baynus.

Open . . . cause--Plead for those who cannot plead for themselves, as the orphan, stranger, &c. (compare Psalm 72:12; Isaiah 1:17).
appointed to destruction--who are otherwise ruined by their oppressors (compare Proverbs 29:14, Proverbs 29:16).

8 Open thy mouth for the dumb,
For the right of all the children of leaving;
9 Open thy mouth, judge righteously,
And do right to the poor and needy.
He is called dumb who suffers the infirmity of dumbness, as עוּר and פּסּח, Job 29:15, is he who suffers the infirmity of blindness or lameness, not here figuratively; at the same time, he who, on account of his youth, or on account of his ignorance, or from fear, cannot speak before the tribunal for himself (Fleischer). With ל the dat. commodi (lxx after Lagarde, μογιλάλῳ; Aquila, Symmachus, Theodotion, ἀλάλῳ; the Venet. after Gebhardt, βωβῷ) אל, of the object aimed at, interchanges, as e.g., 1-Kings 19:3; 2-Kings 7:7, אל־נפשׁם, for the preservation of their life, or for the sake of their life, for it is seldom that it introduces the object so purely as here. And that an infin. such as חלוף should stand as a subst. occurs proportionally seldomer in Hebrews. (Isaiah 4:4; Psalm 22:7; cf. with ה of the artic., Numbers 4:12; Psalm 66:9) than it does in Arab. בּני חלוף in the same way as בּני־עני, 5b, belongs to the Arab. complexion of this proverb, but without its being necessary to refer to the Arab. in order to fix the meaning of these two words. Hitzig explains after khalf, to come after, which further means "to have the disadvantage," in which Zckler follows him; but this verb in Arab. does not mean ὑστερεῖν (ὑστερεῖσθαι), we must explain "sons of him that remains behind," i.e., such as come not forward, but remain behind ('an) others. Mhlau goes further, and explains, with Schultens and Vaihinger: those destitute of defence, after (Arab.) khalafahu he is ranked next to him, and has become his representative - a use of the word foreign to the Hebrews. Still less is the rendering of Gesenius justified, "children of inheritance" = children left behind, after khallafa, to leave behind; and Luther, "for the cause of all who are left behind," by the phrase (Arab.) khallfany'an 'awnih, he has placed me behind his help, denied it to me, for the Kal of the verb cannot mean to abandon, to leave. And that בני חלוף means the opposers of the truth, or of the poor, or the litigious person, the quarrelsome, is perfectly inadmissible, since the Kal חלוף cannot be equivalent to (Arab.) khilaf, the inf. of the 3rd conj., and besides, the gen. after דּין always denotes those in whose favour, not those against whom it is passed; the latter is also valid against Ralbag's "sons of change," i.e., who say things different from what they think; and Ahron b. Josef's "sons of changing," viz., the truth into lies. We must abide by the meaning of the Hebrews. חלף, "to follow after, to change places, pass away." Accordingly, Fleischer understands by חלוף, the going away, the dying, viz., of parents, and translates: eorum qui parentibus orbati sunt. In another way Rashi reaches the same sense: orphans deprived of their helper. But the connection בני חלף requires that we make those who are intended themselves the subject of חלוף. Rightly Ewald, Bertheau, Kamphausen, compare Isaiah 2:18 (and Psalm 90:5., this with questionable right), and understand by the sons of disappearance those whose inherited lot, whose proper fate, is to disappear, to die, to perish (Symmachus: πάντων υἱῶν ἀποιχομένων; Jerome: omnium filiorum qui pertranseunt). It is not men in general as children of frailty that are meant (Kimchi, Meri, Immanuel, Euchel, and others), after which the Venet. τῶν υἱῶν τοῦ μεταβάλλειν (i.e., those who must exchange this life for another), but such as are on the brink of the abyss. צדק in שׁפט־צדק is not equivalent to בּצדק, but is the accus. of the object, as at Zac 8:16, decide justice, i.e., so that justice is the result of thy judicial act; cf. Knobel on Deuteronomy 1:16. ודּין is imper., do right to the miserable and the poor; cf. Psalm 54:3 with Jeremiah 22:16; Jeremiah 5:28. That is a king of a right sort, who directs his high function as a judge, so as to be an advocate [procurator] for the helpless of his people.

The dumb - For such as cannot speak in their own cause, either through ignorance, or because of the dread of their more potent adversaries. Destruction - Who, without such succour from the judges, are like to be utterly ruined.