Though Balak saw the destruction of the Amorites by Israel, yet had he consulted what was said concerning Moab, he might have learnt that Israel had no commission at that time to hurt Moab. On the contrary as Moab sprung from Lot, the LORD had given special command, concerning the preservation of Moab. See Deuteronomy 2:9.
Related Commentaries of Numbers 22:2
Numbers 22:2-4
2 And Balak the son of Zippor saw all that Israel had done to the Amorites.
3 And Moab was sore afraid of the people, because they were many: and Moab was distressed because of the children of Israel.
4 And Moab said unto the elders of Midian, Now shall this company lick up all that are round about us, as the ox licketh up the grass of the field. And Balak the son of Zippor was king of the Moabites at that time.