Question: "What does it mean that the rain falls on the just and the unjust?"
Answer: In Matthew 5:45, as part of the Sermon on the Mount, Jesus says this about God the Father: “He makes his sun rise on the evil and on the good, and sends rain on the just and on the unjust” (ESV). As always, context is the key to understanding this passage. In the verses immediately prior to verse 45, Jesus notes a popular sentiment and then gives a countercultural command: “You have heard that it was said, ‘Love your neighbor and hate your enemy.’ But I tell you, love your enemies and pray for those who persecute you” (verses 43–44). Then, in the first half of verse 45, Jesus gives the rationale behind the command: “That you may be children of your Father in heaven.”
We must not misunderstand Jesus’ statement to mean that one can become a child of God by loving his enemies. We do not earn a place in God’s family by doing this or any other kind of good work. To be a “child” of someone (literally, in the Greek, a “son”) did not necessarily mean that a person was literally a member of the family; rather, a “son” was someone who acted like another person or thing. For instance, James and John were called “sons of thunder” (Mark 3:17) probably because of their potentially hot tempers; they had “thunderous personalities” or perhaps “thunderous tempers.” The Contemporary English Version brings out this meaning of Matthew 5:45: “Then you will be acting like your Father in heaven.” To the extent that a person exhibits a certain characteristic of God, to that extent he will be considered a child of God.
So, how does God love His enemies? There are a number of ways, but in Matthew 5:45 Jesus gives two practical examples. “He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous.” In that agrarian society, good weather was all-important. There are righteous farmers (who would be considered God’s friends) and unrighteous farmers (those who would be considered God’s enemies). Regardless of the farmer’s disposition toward God, God gives sunshine and rain to all the farmers in equal portion. When God gives good sunshine and good rain to an evil farmer, it’s an example of God loving His enemies. God makes no distinction between the evil and the righteous in this instance—He gives good gifts to both of them.
There will be a time of judgment in the future, but, until then, God graciously gives good things, even to those who hate Him. He gives the blessing of rain to the just and the unjust alike. Wicked people, people who mock Him and even deny His existence still get to enjoy good weather, good food, the love of family, and a great many other things. God does not withhold all blessings until a person comes to Him in repentance and faith in Christ. Since God is so generous with His enemies, then we should be as well.