New Defender's Study Bible Notes
15:1 Moab. The prophecy against Moab (descendants of Lot and inveterate enemies of Israel) occupies Isaiah 15 and 16. The Moabites were often invaded and finally disappeared from history shortly before the first coming of Christ. Their land, currently part of the kingdom of Jordan, is now largely desolate, though once quite fruitful.
15:5 My heart shall cry out. God justly must punish Moab for long-continued hostility against the God of their father Lot. Nevertheless, His heart was grieved that this was necessary, and He did leave them a “remnant” (Isaiah 15:9) in their land. Also note Isaiah 16:11,14.