Numbers 11:33-34:

And while the flesh was yet between their teeth, ere it was chewed, the wrath of the LORD was kindled against the people, and the LORD smote the people with a very great plague.
And he called the name of that place Kibroth-hat-ta-a-vah [this means “The Graves of Lust”]: because there they buried the people that lusted.

Notes on Numbers 11:33-34:

This is one of MANY Scriptures that makes it plain that the LORD brought judgment Himself; He did not subcontract the job to Satan, who is not mentioned here.

See also:

Sickness as Chastening and Judgment in the Old Testament

Did God PUT Sickness on Old Testament People or ALLOW the Devil to Do It?