The Lord is declaring that He will pour judgment out on Moab, Judah, and Israel. The Lord list their transgressions in verses 6-8. In verses 9-11 He reminds them of some of the miracles he performed for Israel. In verses 13-16 the Lord tells Israel the punishment that He will cause to come upon them.
The phrase that stood out to me is "Thus saith the Lord; for three transgressions of Moab/Judah/Israel, and for four, I will not turn away the punishment thereof". How easy is it for me to think that I am getting away with something that is not pleasing to God just because after the first time it occurs God does not punish/correct me for it. I have to remember that I will have to give an account for every thought and action that I do. I may not be judged the first time or even the fourth time but I do have to remember that my actions will be dealt with in God's own time and way.
Randal Sheppard