Albert Barnes Commentary Isaiah 30:18

"And therefore will Jehovah wait, that he may be gracious unto you; and therefore will he be exalted, that he may have mercy upon you: for Jehovah is a God of justice; blessed are all they that wait for him." — Isaiah 30:18 (ASV)

And therefore - The sense of the words rendered ‘and therefore,’ may be better expressed by the phrase, ‘yet moreover,’ meaning, that notwithstanding their sins, and the necessity of punishing them, Yahweh would be longsuffering, and would still bring the nation to repentance.

And therefore will he be exalted - Lowth renders this in accordance with a conjecture of Houbigant, ‘Shall he expect in silence, by reading ידוּם yâdûm instead of ירוּם yârûm.’ But there is no authority for this except a single MS. Rosenmuller supposes it means, in accordance with the interpretation of Jarchi, that he would delay, that is, that his mercy would be “long” or his judgment remote. But the sense seems to be, that God would be so forbearing that his character would be “exalted,” that is, that people would have more elevated conceptions of his truth, mercy, and faithfulness.

For the Lord is a God of judgment - He will do what is right. He will spare the nation still; and yet establish among them the true religion, and they will flourish.

Blessed are all they that wait for him - This seems to have been recorded to encourage them, when the threatened calamities would come upon them, to put their confidence in God, and to trust that he would still appear and restore the nation to himself. This verse is the commencement of the annunciation of the blessings which would still be conferred on them. The description of these blessings is continued to Isaiah 30:26.