congregation of the dead - The Rephaim (compare the Proverbs 2:18 note).
Remain - i. e., "He shall find a resting place, but it shall be in Hades."

The man once enlightened, that wandereth out of the way of understanding, in which he had walked, shall remain - have a permanent residence - in the congregation of the dead; רפאים rephaim, the lost; either separate spirits in general, or rather the assembly of separate spirits, which had fallen from primitive rectitude; and shall not be restored to the Divine favor; particularly those sinners who were destroyed by the deluge. This passage intimates that those called rephaim are in a state of conscious existence. It is difficult to assign the true meaning of the word in several places where it occurs: but it seems to mean the state of separate spirits, i.e., of those separated from their bodies, and awaiting the judgment of the great day: but the congregation may also include the fallen angels. My old MS. Bible translates, The man that errith fro the wei of doctrine, in the felowschip of geantis schal wonnen.

The man that wandereth out of the way of understanding,.... The way of getting understanding, the good ways and word of God; that wanders from the house of God, the assembly of the saints, where the Gospel is preached, and the ordinances are administered; that, instead of attending on them, where he might gain the understanding of divine and spiritual things, wanders about in the fields, gets into bad company, walks with them in their ways, and turns to his own, as a sheep that goes astray: he
shall remain in the congregation of the dead; among those that are spiritually dead, dead in trespasses and sins; such an one he himself is, and such he is like to continue, and not be written among the living in Jerusalem; or among those who die the second and eternal death, among the damned in hell; so Jarchi interprets it of the congregation of hell; and a large congregation that will be, but dreadful to have an abode with them. The words are rendered by the Septuagint, and the versions that follow that, "shall rest in the congregation of the giants"; which some interpret of devils, and others of the giants of the old world (b), damned spirits: resting with them does not design peace and quietness, for there will be none there; but a fixed settled abode, in opposition to wandering, in the preceding clause.
(b) See Mede's Discourse 7. p. 32.

Of all wanderers in the ways of sin, those are in the most dangerous condition who turn aside into the ways of darkness. Yet there is hope even for them in the all-sufficient Saviour; but let them flee to him without delay.

the way of understanding--(Compare Proverbs 12:26; Proverbs 14:22).
remain--that is, rest as at a journey's end; death will be his unchanging home.

16 A man who wanders from the way of understanding,
Shall dwell in the assembly of the dead.
Regarding השׂכּל, vid., Proverbs 1:3; and regarding רפאים, Proverbs 2:18. The verb נוּח means to repose, to take rest, Job 3:13, and to dwell anywhere, Proverbs 14:33; but originally like (Arab.) nâkh and hadd, to lay oneself down anywhere, and there to come to rest; and that is the idea which is here connected with ינוּח, for the figurative description of יאבד or ימוּת is formed after the designation of the subject, 16a: he who, forsaking the way of understanding, walks in the way of error, at length comes to the assembly of the dead; for every motion has an end, and every journey a goal, whether it be one that is self-appointed or which is appointed for him. Here also it is intimated that the way of the soul which loves wisdom and follows her goes in another direction than earthwards down into hades; hades and death, its background appear here as punishments, and it is true that as such one may escape them.

Shall remain - Shall, without repentance, be condemned to eternal death.