Numbers 25:6-9

6And behold, one of the people of Israel came and brought a Midianite woman to his family, in the sight of Moses and in the sight of the whole congregation of the people of Israel, while they were weeping in the entrance of the tent of meeting.

7When Phinehas the son of Eleazar, son of Aaron the priest, saw it, he rose and left the congregation and took a spear in his hand

8and went after the man of Israel into the chamber and pierced both of them, the man of Israel and the woman through her belly. Thus the plague on the people of Israel was stopped.

9Nevertheless, those who died by the plague were twenty-four thousand.