Adam Clarke Bible Commentary
The cause which I knew not I searched out - When any thing difficult occurred, I did not give it a slight consideration; I examined it to the bottom, whatever pain, time, and trouble it cost me, that I might not pronounce a hasty judgment.
Jamieson-Fausset-Brown Bible Commentary
So far was I from "breaking the arms of the fatherless," as Eliphaz asserts (Job 22:9), I was a "father" to such.
the cause which I knew not--rather, "of him whom I knew not," the stranger (Pro 29:7 [UMBREIT]; contrast Luk 18:1, &c.). Applicable to almsgiving (Psa 41:1); but here primarily, judicial conscientiousness (Job 31:13).
John Gill Bible Commentary
I was a father to the poor,.... Not in a literal sense; for his children were rich as well as himself, while he had them; but in a civil sense, he was the patron of the poor; he was an advocate for them, he took their part, he pleaded their cause, defended their persons, and secured the little property they had; he had the pity and compassion of a father for them, and supplied their wants; he fed them and clothed them; he did not eat his morsel alone, but gave them part of it, and warmed them with the fleece of his flock:
and the cause which I knew not I searched out; any cause that was brought before him, he knew thing of before, and which, upon the opening of it, did not appear plain and easy, but had its difficulties; this he closely examined, and searched thoroughly into the merits of, till it appeared plain to him on which side the truth and justice of it lay; he did not hurry it over, and pass sentence, having only in a superficial manner considered it, as is too often the case; but after a long examination of the contending parties, and of the witnesses on both sides, to whom he gave an impartial hearing, he pronounced the decisive sentence; see Pro 25:2. Some think this refers to his diligent search and inquiry after causes that were not brought before him; he did, not wait for application to be made to him, but hearing of, or upon inquiry finding, that there were persons oppressed and distressed by cruel men, he of himself voluntarily offered his assistance, searched into their cause, made himself master of it, and freed them from their distresses; so different were his behaviour and character from that of the unjust judge, Luk 18:1; though others, choose to render the words, "the cause of him that I knew not", &c. (t); of a stranger, of one that he had never seen before, of one that was most unknown to him in the world; the cause of such an one he took as, much pains with to get the true knowledge of, and do justice to, as of the dearest relation, the nearest neighbour, and the most intimate friend and acquaintance that he had.
(t) "quem non cognoveram", Junius & Tremellius, Michaelis; "ignotissimi", Schultens.