Jamieson, Fausset and Brown on Isaiah 30:18

18. therefore--on account of your wicked perverseness (Is 30:1, 2, 9, 15, 16), Jehovah will delay to be gracious [Horsley]. Rather, wait or delay in punishing, to give you time for repentance (Is 30:13, 14, 17) [Maurer]. Or, "Yet therefore" (namely, because of the distress spoken of in the previous verses; that distress will lead the Jews to repentance, and so Jehovah will pity them) [Gesenius].

be exalted--Men will have more elevated views of God's mercy; or else, "He will rise up to pity you" [G. V. Smith]. Or (taking the previous clause as Maurer, "Therefore Jehovah will delay" in punishing you, "in order that He may be gracious to you," if ye repent), He will be far removed from you (so in Psa 10:5, far above out sight); that is, He will not immediately descend to punish, "in order that He may have mercy," &c.

judgment--justice; faithfulness to His covenant.

wait--compare Is 30:15, wait, namely, for His times of having mercy.