Numbers 23 - Balak seeks to bribe Balaam into calling for a curse against Israel. He obviously didn't listen to what God said to Abram back in Genesis 12 that those who would seek to curse Israel would be cursed themselves. Later in the Bible we read of the true nature of Balaam. God forced him to say what God wanted him to say. Instead of calling for a curse, Balaam prayed for God's blessing on His people.
Numbers 24 - Balak was increasingly frustrated with Balaam's refusal to curse Israel. But Balaam was still obligated to God to bless the Jews. He even spoke of their future and that they would have a King greater than Balak, which some see as a referral to the coming Messiah. Balak attempts to send Balaam packing, but Balaam has one more word of rebuke to Balak!
Numbers 25 - Though it doesn't say so here, Balaam causes the Moabite women to seduce the Israelite men into immoral behavior. Thus Balaam, who couldn't curse Israel, was able to corrupt that nation. The devil knows that if he can't defeat us he will try to defile us. We must watch out for Satan's influence on our morality. We see in this passage that Eleazar's son, Phineas, became enraged at the sin of Israel and he delivered severe judgment against one of the Israelite men who blatantly committed sin right in front of Moses. God commended Phineas for this zealous act to turn God's fury away from Israel.