Israel's idolatry of Baal of Peor. The zeal of Phinehas for the Lord.
And Israel camped in Shittim. Then the people took to whoring with the daughters of the Moabites, they invited the people to make offerings to their gods, they ate and prayed to them. Israel yoked itself to Baal of Peor. The Lord's wrath rose against Israel and he spoke to Moses: take all the leaders of this people and hang them before the Lord in broad daylight so that the fierceness of the Lord's anger may be turned away from Israel. And Moses commanded the judges of Israel: kill all that have yoked themselves to these gods. A man of the tribe of the Israelites came and brought amongst his brothers a “Midianite” woman before the eyes of Moses and the community that wept before the tabernacle. When Phinehas, son of Eleazar saw this he stood up from the community, took a skewer and followed the Israelite man into the chamber and stabbed it through both of them. The plague among the Israelites ceased. 24,000 had been killed had been killed by the plague.
The Lord spoke to Moses: Phinehas has quenched my wrath with his zeal, that I have not exterminated the Israelites in my zeal. Therefore say: behold, I give him my covenant of peace, which gives him the lasting priesthood, for he is zealous for a god, has made atonement for Israel. The one who was stabbed was named Zimri, the son of Salu. The leader of a tribe. The woman was named Kozbi, daughter of Zur, a tribal chief of the Midianites. The Lord spoke to Moses: injure the Midianites and conquer them, for they have done injury to you with their ploy through Kozbi and Peor.