What's the big idea?

The people of Judah began to be exiled from the Promised Land in 605 BC, returning from Babylon seventy years later. By the time of Malachi, they had been back in the land for more than a hundred years and were looking for the blessings they expected to receive when they returned. Though the temple had been rebuilt, the fervor of those early returning Israelites gave way to a thorough apathy for the things of God. This led to rampant corruption among the priesthood and a spiritual lethargy among the people.

Malachi came along at a time when the people were struggling to believe that God loved them (Malachi 1:2). The people focused on their unfortunate circumstances and refused to account for their own sinful deeds. So God pointed the finger back at them, and through Malachi, God told the people where they had fallen short of their covenant with Him. If they hoped to see changes, they needed to take responsibility for their own actions and serve God faithfully according to the promise their fathers had made to God on Mount Sinai all those years before. 

(Chuck Swindoll)