Balak was the king of Moab and the son of Zippor. During the Exodus, he became afraid when he saw the Israelites defeat the Amorites and their king, Sihon. Thinking that he could not stop the Israelites through war, he tried to defeat them by having the corrupt prophet Balaam curse them.
Num 22:2Now Balak the son of Zippor saw all that Israel had done to the Amorites.Num 22:3And Moab was in great dread of the people, because they were many. Moab was overcome with fear of the people of Israel.Num 22:4And Moab said to the elders of Midian, “This horde will now lick up all that is around us, as the ox licks up the grass of the field.” So Balak the son of Zippor, who was king of Moab at that time,Num 22:5sent messengers to Pethor, which is near the River in the land of the people of Puhor, to summon Balaam the son of Beor, saying, “Behold, a people has come out of Egypt. They cover the face of the earth and are dwelling opposite me.Num 22:6Come now, curse this people for me, since they are too mighty for me. Perhaps I shall be able to defeat them and drive them from the land, for I know that he whom you bless is blessed, and he whom you curse is cursed.”
However, by God's grace, who watched over the Israelites, Balaam was unable to curse them and instead blessed them.
For more details, see Balaam.