The first reading chosen by the lectionary is this passage from Malachi which is usually dated to the Persian period. The people have known exile, have felt that they had been forgotten by God, and are looking toward a word from God.
Christians read this passage in Malachi as a foretelling of the coming of Christ.
After the fire that refines and purifies, the offering of Judah and Jerusalem will be as pleasing as it once was. (How does this promise relate to our situation? Should we translate the refinement as something that happens after death? Or, should we go ahead and repent immediately?)
Allen & Williamson in their Preaching the Old Testament see "the refiner's fire" to be a simile for the transformative love of God:
We are so accustomed to speaking of God's justifying, forgiving, and redeeming grace that we sometimes forget the basic point that God has a purpose in all that God does, and the purpose is that all people should have life and well-being (2:5). Yet clearly they cannot as long as we insist on and persist in living in ways that lead to death and curse. God's love is freely given to each and all, but it is a love that gives and calls us to become people who love God with all our selves and our neighbors as ourselves and to act accordingly in relation to our neighbors.Lectio Divina: Malachi 3:2