Numbers 25:9 (BSB)

but those who died in the plague numbered 24,000.

From Numbers 25. Also in the ESV.

Commentary on Numbers 25:9

• John Calvin (Reformed), Calvin's Commentaries on Numbers 25:9: 9. And those that died in the plague. Paul, when he says that only twenty-three thousand died, appears to differ from Moses; but we know that the exact account of numbers is not always observed, and it is probable that about twenty-four thousand were slain. Paul, therefore, subtracted one thousand, and was content with the lesser number; C.
• Matthew Henry (Presbyterian), Matthew Henry's Complete Commentary on Numbers 25:6-15: Here is a remarkable contest between wickedness and righteousness, which shall be most bold and resolute; and righteousness carries the day, as no doubt it will at last. I. Never was vice more daring than it was in Zimri, a prince of a chief house in the tribe of Simeon.
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on Numbers 25:9: And those that died in the plague were twenty and four thousand. The apostle says 23,000 Co1 10:8. Moses includes those that were hanged against the sun, in the time of the plague, as well as those that were taken off by it, even all that died on this account; the apostle only those that "fell", which cannot with propriety be said of those that...
• Jamieson-Fausset-Brown (Reformed), Commentary Critical and Explanatory on the Whole Bible on Numbers 25:9: those that died in the plague were twenty and four thousand--Only twenty-three thousand perished (Co1 10:8) from pestilence. Moses includes those who died by the execution of the judges [Num 25:5].