Malachi - Chapter 3
The Last Prophecy
G-d says that He sends His messenger (an angel? Malachi himself?) to clear the way before Him. G-d will come to the Temple and the angel to punish the wicked will arrive. Who will be able to stand before this angel, who will be like a fire that refines silver by removing the defects? The kohanim (priests) will be refined and purified until they are like gold and silver, serving G-d with righteousness. When this happens, the sacrifices of the nation will be as pleasing to G-d as they were in the "good old days." (This is the closing sentiment of the Amidah prayer.)
G-d will make quick work of sorcerers, adulterers, people who swear falsely, those who don't pay their workers promptly, and those who oppress widows, orphans and converts. These people act this way because they have no fear of G-d. G-d has not changed His mind; He still loves righteousness and hates injustice. The people have not reached the end of their journey; they still have judgment in the Next World. The people have neglected G-d's Torah for a long time. Now He says, "Return to Me and I will return to you." The people ask how they can return to Him. Would a person rob his god? Obviously not, but they have "robbed" G-d via improper use of tithes and other sacred gifts. G-d sends a curse that affects prosperity because of this. If the people will be diligent with their tithes, G-d will bless their handiwork - He even invites the people to test Him when it comes to this, something we are not permitted to do with other mitzvos. When this abundance is seen, Israel will be praised by the other nations.
Getting back to the people's indiscretions, they said that there was no reward for serving G-d, since man is beneath His notice, so why bother? The people saw crime pay to such a degree that the criminals became heroes to them. The G-d-fearing people strengthened themselves not to be swayed by these arguments. G-d heard these people and metaphorically "inscribed" the names of those who defended His honor. They are the ones who will ultimately be resurrected. People will be able to tell the difference between the righteous and the evil then! The sun will be like an oven and the wicked will be consumed like straw, leaving no trace. But the same sun will be a source of healing for the righteous, who will walk over the wicked as if they were ash.
The Jews are reminded to keep the Torah, which G-d sent through Moses. G-d will send the people Elijah the prophet (who ascended to Heaven alive back in II Kings chapter 2) prior to the day of judgment. Elijah will turn the hearts of parents and children to one another, causing both to turn to G-d. If they won't return to G-d, then He will strike the world with great destruction. (In order to avoid ending the book on a bad note, the practice is to repeat the previous verse about Elijah turning the hearts of parents and children.)
The verse about Elijah may be familiar as it is sung as a song ("hinei Anochi sholeiach lachem..."). However, the actual verse does not say "Eliyahu," as people are accustomed to sing. The verse uses the less familiar version "Eliya." This is similar to other such variations, such as Yeshaya/Yeshayahu. (You'll note that the English equivalents - Isaiah, Jeremiah, Hezekiah, etc. - typically do not reflect the "hu" suffix.)
This prophecy is the last one in the Bible. With the end of Malachi, we conclude the Books of the Prophets. The Bible continues with Psalms and the other Writings. These works were written with Divine inspiration rather than through out-and-out prophecy.