We can see that James here castigates a group of rich people. Why does he do so? He builds up a list of reasons in verses 4 to 6. The rich he has in mind are guilty of withholding wages from their workers, of living luxuriously, and of having condemned and killed a righteous person. So we can deduce that the rich here are opposed to the Christian faith. Probably they had been the cause of the persecution that James’ readers were experiencing.
Given that only a few years had passed since the crucifixion of Jesus, it is possible that the James is referring to Jesus when he writes that the rich had killed a righteous person. Whether James means this or not, we know that Jesus had said to his disciples that his opponents would persecute him and would persecute them.
James urges the rich here to commence weeping and howling, but he is not suggesting repentance. Instead, he is describing cries of despair because of divine judgement. The divine judgement is twofold, with one aspect occurring in the present and the other aspect in the future. Both forms of judgement come from God. In the present, he ensures that their possessions will be destroyed, even the precious metals that they might imagine would not erode; and in the future, he will deal with them severely (they are like animals being prepared for slaughter).
What does this passage say to us? First, it is unlikely that the rich oppressors would have read this passage because the letter was not sent to them. So, in a sense, this description of the fate of the rich oppressors is for the information of the oppressed. Maybe the sufferers were wondering if God had forgotten them, and these verses are a reminder that he knows what had happened to them and would yet take action.
Second, God will judge those who oppress the poor. We cannot limit the unpaid in verse 4 to Christians, although among the unpaid there were believers. James points out that the wages that were kept back spoke loudly in heaven. The rich may have imagined that the poor had no voice, but in fact the laments of the harvesters were listened to by God and he will yet deal with it.
James’ words here about the sinful behaviour of the rich are expressions of righteous indignation against evil practices. In doing this, he was giving to us an example of the proper use of the tongue. His response justifies the occasions when the church speaks out against injustice; indeed, his response indicates that the church is required to say that such behaviour is wrong. James would have been aware that many of the Old Testament prophets used similar words about injustice, and they have been models for many Christians to do the same.