Numbers 25:1, 6-8

Israel settled and remained in Shittim, and the people began to play the prostitute with the women of Moab [by being unfaithful to God].

Then one of the Israelites came and presented to his relatives a Midianite woman, in the sight of Moses and the whole congregation of the Israelites, while they were weeping [over God’s judgment] at the doorway of the Tent of Meeting (tabernacle). When Phinehas the son of Eleazar, the son of Aaron the priest, saw this, he left the congregation and took a spear in his hand, and he went after the man of Israel into the tent, and pierced both of them through the body, the man of Israel and the woman. Then the plague on the Israelites stopped.