What does 2 Samuel 24:3 mean?

But Joab pushed back, saying, 'May the Lord multiply the people a hundred times over, and may you live to see it, my king. But why do you want to do this?' 2 Samuel 24:3 - Modern Text Bible

(Joab senses that counting the people is wrong, maybe because it shows a lack of faith. He tries to talk David out of it.)