Matthew Henry Commentary Numbers 25:1-5

"And Israel abode in Shittim; and the people began to play the harlot with the daughters of Moab: for they called the people unto the sacrifices of their gods; and the people did eat, and bowed down to their gods. And Israel joined himself unto Baal-peor: and the anger of Jehovah was kindled against Israel. And Jehovah said unto Moses, Take all the chiefs of the people, and hang them up unto Jehovah before the sun, that the fierce anger of Jehovah may turn away from Israel. And Moses said unto the judges of Israel, Slay ye every one his men that have joined themselves unto Baal-peor." — Numbers 25:1-5 (ASV)

The friendship of the wicked is more dangerous than their hostility, for no one can prevail against God's people if they are not overcome by their inherent lusts. Nor can any enchantment hurt them, other than the enticements of worldly interests and pleasures. Here is the sin of Israel, to which they were enticed by the daughters of Moab and Midian. Those are our worst enemies who draw us to sin, for that is the greatest harm anyone can do us. Israel's sin did what all Balaam's enchantments could not do: it set God against them. Diseases are the fruits of God's anger and the just punishments of prevailing sins, and one infection follows another. Ringleaders in sin should be made examples of justice.