All modes of teaching - the stern rebuke or the smiling speech - are alike useless with the "foolish" man; there is "no rest." The ceaseless cavilling goes on still.

Whether he rage or laugh - Coverdale translates, "Yf a wyse man go to lawe with a foole, whether he deale with him frendly or roughly he geteth no rest."

[If] a wise man contendeth with (c) a foolish man, whether he rageth or laugheth, [there is] no rest.
(c) He can hear no admonition no matter how it is spoken.

If a wise man contendeth with a foolish man,.... Enters into a controversy with him, either by word or writing, in order to convince him of his folly and wickedness, of his errors and mistakes;
whether he rage or laugh, there is no rest; that is, either whether the fool is angry with the wise man, and rages at him and abuses him, and calls him names, or laughs at him, and scoffs at all his arguments, reasons, and advice; yet the wise man does not cease from proceeding in the contest with him; or he is not dejected and cast down, and discouraged; or, as the Targum is,
"he is not broken;''
but patiently bears his wrath fury, his scoffs and jeers: or else whether the wise man deals roughly or gently with the feel, in a morose or in a mere jocose way: it has no upon him; he is never the better for it; he does not acquiesce or rest in what he says like the Pharisees in Christ's time, who are compared to surly children: who, when "piped to, danced not"; and, when "mourned to, lamented not"; see Gill on Matthew 11:16, and See Gill on Matthew 11:17. The design of the proverb is to show, that all labour to reclaim a fool from his folly is lost, let a man take what methods he will, Proverbs 27:22.

If a wise man dispute with a conceited wrangler, he will be treated with anger or ridicule; and no good is done.

contendeth--that is, in law.
whether . . . laugh--The fool, whether angry or good-humored, is unsettled; or referring the words to the wise man, the sense is, that all his efforts, severe or gentle, are unavailing to pacify the fool.

9 If a wise man has to contend with a fool,
He the fool rageth and laugheth, and hath no rest.
Among the old translators, Jerome and Luther take the "wise man" as subject even of the second line, and that in all its three members: vir sapiens si cum stulto contenderit, sive irascatur sive reideat, non inveniet requiem. Thus Schultens, C. B. Michaelis, Umbreit, Ewald, Elster, and also Fleischer: "The doubled Vav is correlative, as at Exodus 21:16; Leviticus 5:3, and expresses the perfect sameness in respect of the effect, here of the want of effect. If the wise man, when he disputes with a fool, becomes angry, or jests, he will have no rest, i.e., he will never bring it to pass that the fool shall cease to reply; he yields the right to him, and thus makes it possible for him to end the strife." But the angry passion, and the bursts of laughter alternating therewith, are not appropriate to the wise man affirming his right; and since, after Ecclesiastes 9:17, the words of the wise are heard בּנחח, the ואין נחת [and there is no rest] will cause us to think of the fool as the logical subject. So far correctly, but in other respects inappropriately, the lxx ἀνὴρ σοφὸς κρινεῖ ἔθνη (after the expression עם, i.e., עם, instead of את), ἀνὴρ δὲ φαῦλος (which אישׁ אויל does not mean) ὀργιζόμενος καταγελᾶται καὶ οὐ καταπτήσσει (as if the words were ולא יחת).
(Note: According to this the Targum ולא מתתּבר (he remains obstinate), according to which the ולא מתתפיר (he does not lose his wits) of the Peshito is perhaps to be corrected. The distribution of the subjects is obscure.)
The syntactical relation would be simpler if נשׁפּט in 9a were vocalized as a hypothetical perfect. But we read for it the past נשׁפּט. Ewald designates 9a as a conditional clause, and Hitzig remarks that the Lat. viro sapiente disceptante cum stulto corresponds therewith. It marks, like 1-Samuel 2:13; Job 1:16, the situation from which there is a departure then with perf. consec.: if a wise man in the right is in contact with a fool, he starts up, and laughs, and keeps not quiet (supply לּו as at Proverbs 28:27), or (without לו): there is no keeping quiet, there is no rest. The figure is in accordance with experience. If a wise man has any controversy with a fool, which is to be decided by reasonable and moral arguments, then he becomes boisterous and laughs, and shows himself incapable of quietly listening to his opponent, and of appreciating his arguments.

Whether - Whether he, the wise man, deal sharply with him, or mildly, there is no rest, no end or fruit of the debate.