Therefore - לכן lākên, "certainly, truly." In view of what has been just said. Or perhaps the word means merely certainly, truly.
Do my thoughts cause me to answer - This is variously rendered. The Vulgate renders it, Idcirco cogitationes meae variae succedunt sibi, et mens in diversa rapitur - "Therefore my various thoughts follow in succession, and the mind is distracted." The Septuagint, "I did not suppose that thou wouldst speak against these things, and you do not understand more than I." How this was ever made from the Hebrew it is impossible to say. On the word "thoughts," see the notes at Job 4:13. The word denotes thoughts which divide and distract the mind; not calm and collected reflections, but those which disturb, disconcert, and trouble. He acknowledges that it was not calm reflection which induced him to reply, but the agitating emotions produced by the speech of Job. The word rendered "cause me to answer" (ישׁיבוּני yeshı̂ybûnı̂y), "cause me to return" - and Jerome understood it as meaning that his thoughts returned upon him in quick and troublesome succession, and says in his Commentary on Job, that the meaning is, "I am troubled and agitated because you say that you sustain these evils from God without cause, when nothing evil ought to be suspected of God."
And for this I make haste - Margin, "my haste is in me." The meaning is, "the impetuosity of my feelings urges me on. I reply on account of the agitation of my soul, which will admit of no delay." His heart was full, and he hastened to give vent to his feelings in impassioned and earnest language.

Therefore do my thoughts - It has already been observed that Zophar was the most inveterate of all Job's enemies, for we really must cease to call them friends. He sets no bounds to his invective, and outrages every rule of charity. A man of such a bitter spirit must have been, in general, very unhappy. With him Job is, by insinuation, every thing that is base, vile, and hypocritical. Mr. Good translates this verse thus: "Whither would my tumult transport me? And how far my agitation within me?" This is all the modesty that appears in Zophar's discourse. He acknowledges that he is pressed by the impetuosity of his spirit to reply to Job's self-vindication. The original is variously translated, but the sense is as above.
For this I make haste - ובעבור חושי בי ubaabur chushi bi, there is sensibility in me, and my feelings provoke me to reply.

Therefore do my thoughts cause me to answer,.... Or "to return" (a) and appear upon the stage again, and enter the lists once more with his antagonist; he suggests as if he had intended to have said no more in this controversy, but observing what Job had said last, could not forbear replying: "therefore" because he had represented him and his friends as cruel persecutors of him, as men devoid of all humanity, pity, and compassion, and endeavoured to terrify them with the punishments of the sword, and the judgment of God to come; these occasioned many "thoughts" in him, and those thoughts obliged him to give an answer; they came in so thick and fast upon him, that out of the abundance, his heart suggested to him he could not but speak, he was full of matter, and the spirit within him, the impulse upon his mind, constrained him to make a reply; and he seems desirous of having it understood that his answer proceeded from thought; that he did not speak without thinking, but had well weighed things in his mind; and what he was about to say was the fruit of close thinking and mature deliberation:
and for this I make haste; because his thoughts crowded in upon him, he had a fulness of matter, an impulse of mind, promptitude and readiness to speak on this occasion, and for fear of losing what was suggested to him, he made haste to give in his answer, perhaps observing some other of his friends rising up before him. The Targum is,
"because my sense is in me;''
and so other Jewish writers (b); be apprehended he had a right sense of things, and understood the matter in controversy full well, and therefore thought it incumbent on him to speak once more in it: Gussetius (c) renders it, "because of my disquietude"; the uneasiness of his mind raised by what Job had said, that he would have them know and consider there was a judgment; and he intimates he had considered it, and was fearful that should he be silent, and make no reply, God would condemn him in judgment for his silence; and therefore he was in a hurry to make answer, and could not be easy without it; and for his reasons for so doing he further explains himself in Job 20:3.
(a) "reducunt me, q. d. in scenam"; Cocceius, Junius & Tremellius, Piscator, Drusius. (b) Ben Gersom, Bar Tzemach, Sephorno; and so Montanus. (c) Ebr. Comment. p. 246.

REPLY OF ZOPHAR. (Job 20:1-29)
Therefore--Rather, the more excited I feel by Job's speech, the more for that very reason shall my reply be supplied by my calm consideration. Literally, "Notwithstanding; my calm thoughts (as in Job 4:13) shall furnish my answer, because of the excitement (haste) within me" [UMBREIT].

Therefore - For this thy severe sentence. Make haste - I speak sooner than I intended. And possibly interrupted Job, when he was proceeding in his discourse.