Don’t mistake this phrase. After being justified through faith, “we have peace with God”. It does not mean we receive peace from God. It doesn’t mean a warm, happy, fuzzy feeling. The “peace” in this context is in contrast to what previously was there: alienation, antagonism, and conflict with God. As Paul says in the following verses: “For if, when we were God’s enemies, we were reconciled to him through the death of his Son, how much more, having been reconciled, shall we be saved through his life!”
Remember the parable from yesterday's reading in Matthew 21? Jesus tells a parable of a land owner who plants a vineyard and rents it to some farmers. They rebel, beating and killing every servant sent to them from the master. Finally they murder the master's own son (predicting his own death). Now this is a parable directed at the Israelites and even more so at the Pharisees. Their rejection of God and the son he sent results in this pronouncement: "the kingdom of God will be taken away from you and given to a people who will produce its fruit".
But if Romans 5 is right, we are in the same camp. We are enemies just like the rebels and murderers. We are the rebels and murderers. But do you notice the common theme in both passages?
The death of the son.
Ironic, isn't it? The death of the son is at the same time the height of the enemies' rebellion (Matt. 21), and the source of reconciliation (Rom. 5). And the question is, do you still remain in rebellion and stand guilty of the death of the son? Or do you have peace with God in the death (and life) of the son?