isaiah 18:4 For so the LORD said unto me, I will take my rest, and I will consider in my dwelling place like a clear heat upon herbs, and like a cloud of dew in the heat of harvest. - Free Bible Online

      4. take . . . rest . . . consider--I will calmly look on and not interpose, while all seems to promise success to the enemy; when figuratively, "the sun's heat" and "the night dews" ripen their "harvest"; but "before" it reaches its maturity I will destroy it (Isa 18:5; Ec 8:11, 12).
      like a clear heat--rather, "at the time of the clear (serene) heat" [MAURER].
      upon herbs--answering to "harvest" in the parallel clause. MAURER translates, "in the sunlight" (Job 31:26; 37:21; Hab 3:4).
      like . . . dew--rather, "at the time of the dew cloud." God's "silence" is mistaken by the ungodly for consent; His delay in taking vengeance for forgetfulness (Ps 50:21); so it shall be before the vengeance which in the last day shall usher in the restoration of the Jews (Isa 34:1-8; 57:11, end of the verse, 2Pe 3:3-10).

JFB.