Charles Spurgeon Commentary Isaiah 48:18-19

"Oh that thou hadst hearkened to my commandments! then had thy peace been as a river, and thy righteousness as the waves of the sea: thy seed also had been as the sand, and the offspring of thy bowels like the grains thereof: his name would not be cut off nor destroyed from before me." — Isaiah 48:18-19 (ASV)

All manner of possible good would have been yours had you not rebelled against God; and since you have lost it, God grieves that it is so.