The first reading gives us a legend about three choices that God had his prophet propose to David. In punishment for his sin of pride David could choose either a three-year famine for his people, a three-day flight from his enemy for himself, or a three-day pestilence for his people. In this legend David chose the three-day pestilence; and it resulted in an infection that took the lives seventy thousand of his people.
This tall story is like Monday’s Gospel legend about two thousand swine, possessed by devils, rushing down a hill to deaths by drowning. Both stories are too weird to be believed, and God does not want us to believe them. Each is a popular legend that was given a place in the Bible because it illustrated an important fact. The legend about the two thousand swine not wanting to live after they had been possessed by devils is a story told to show how awful it is to live a life opposed to God. The legend of David being given three terrible choices to atone for his opposing God tells us that opposing Gold is no small crime.