What does the verse mean that God sends rain on the just and on the unjust?

Jesus is saying that our Father in heaven DOES GOOD to the just AND the unjust!

Jesus is teaching that it WAS said, you shall love your neighbour, and HATE your enemy. Jesus said, INSTEAD of hating our enemies, we are to LOVE our enemies. We are to BLESS them that curse us, DO GOOD to them that hate us, and PRAY for them which despitefully use us and persecute us. We are to DO GOOD not only to the just, but also to the unjust! We are to DO GOOD not only to the good, but also DO GOOD to the evil!

Why?

Because we are to be as our Father which is in heaven.

Jesus explains our Father makes His sun to rise on the evil AND on the good, and sends rain on the just AND on the unjust. God DOES GOOD to BOTH the just AND to the unjust! He BLESSES BOTH with His sun and His rain, whether they are GOOD or EVIL, JUST or UNJUST! God does not keep back His rain from the unjust – He BLESSES them, just as He BLESSES the just with His rain!

               

 "Ye have heard that it hath been said, Thou shalt love thy neighbour, and hate thine enemy. But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you; That ye may be the children of your Father which is in heaven: for he maketh his sun to rise on the evil and on the good, and sendeth rain on the just and on the unjust. For if ye love them which love you, what reward have ye? do not even the publicans the same? And if ye salute your brethren only, what do ye more than others? do not even the publicans so? Be ye therefore perfect, even as your Father which is in heaven is perfect." - Matthew 5:43-48 KJV