Who did God tell Moses to vex and smite in Numbers 25?

The Midianites

And the LORD spake unto Moses, saying,

Vex the Midianites, and smite them:

For they vex you with their wiles, wherewith they have beguiled you in the matter of Peor, and in the matter of Cozbi, the daughter of a prince of Midian, their sister, which was slain in the day of the plague for Peor's sake. Numbers 25:16-18