| Barnes' Notes on the Bible Or, "He hath" made me to dwell "in darkness," i. e. in Sheol or Hades, "as those" forever "dead."
Gill's Exposition of the Entire BibleHe hath set me in dark places,.... In the dark house of the prison, as the Targum; in the dark dungeon where the prophet was put; or the captivity in which the Jews were, and which was like the dark grave or state of the dead; and hence they are said to be in their graves, Ezekiel 37:12. Christ was laid in the dark grave literally: as they that be dead of old: that have been long dead, and are forgotten, as if they had never been; see Psalm 88:5; or, "as the dead of the world" (f), or age; who, being dead, are gone out of the world, and no more in it. The Targum is, "as the dead who go into another world.'' (f) , Sept. "quasi mortuos seculi", Montanus, Calvin.
Keil and Delitzsch Biblical Commentary on the Old TestamentLamentations 3:6 is a verbatim reminiscence from Psalm 143:3. מחשׁכּים is the darkness of the grave and of Sheol; cf. Psalm 88:7. מתי עולם does not mean "the dead of antiquity" (Rosenmller, Maurer, Ewald, Thenius, etc.), but, as in Psalm 143:3, those eternally dead, who lie in the long night of death, from which there is no return into this life. In opposition to the explanation dudum mortui, Gerlach fittingly remarks, that "it makes no difference whether they have been dead long ago or only recently, inasmuch as those dead and buried a short time ago lie in darkness equally with those who have long been dead;" while it avails nothing to point to Psalm 88:5-7, as Ngelsbach does, since the special subject there treated of is not those who have long been dead.
Geneva Study BibleHe hath set me in dark places, as they that be dead of old.
Jamieson-Fausset-Brown Bible Commentary6. set me-Henderson refers this to the custom of placing the dead in a sitting posture. dark places-sepulchers. As those "dead long since"; so Jeremiah and his people are consigned to oblivion (Ps 88:5, 6; 143:3; Eze 37:13). Gimel.
Matthew Henry's Concise Commentary3:1-20 The prophet relates the more gloomy and discouraging part of his experience, and how he found support and relief. In the time of his trial the Lord had become terrible to him. It was an affliction that was misery itself; for sin makes the cup of affliction a bitter cup. The struggle between unbelief and faith is often very severe. But the weakest believer is wrong, if he thinks that his strength and hope are perished from the Lord. | 
