The Lord makes a rather startling revelation in speaking about the Father's mercy and providence: "He makes his sun rise on the evil and on the good, and sends rain on the just and on the unjust" (Matthew 5:45). God doesn't withhold the benefits of sun and rain from people just because they are wicked or unjust. He would like them to recognize and acknowledge his magnanimity and turn to Him with gratitude and a resolution to change. Yet He wants to manifest to the world that his love is not conditioned by our lack of response. We can condemn ourselves by not responding to his love, but that doesn't mean He loves us any less.
Did Jesus tell us this just to show us how wonderful the Father is? Yes, but more than that. The whole point of it is that we are to become children of our heavenly Father through imitation of his boundless love, and thus to "be perfect, as your heavenly Father is perfect" (5:48). From most perspectives on the meaning of "perfection," this would be impossible. As humans, the countless perfections that belong to the divine nature are for us wholly out of reach. But the Greek word from which "perfection" stems is telos, which connotes completeness, a goal or end. When Jesus died, St John tells us that He said, Tetelestai--it is finished, completed, the goal of his incarnation and sacrifice has been attained. So in one sense, what Jesus is saying is that we have to have the same goals as the Father, striving until we reach the fullness or completion of all that is possible to us with the help of divine grace.
To be able to achieve the goals of the Father for his children in this world, we have to love as He loves. When Jesus said we have to be children of the Father, it was in the context of loving and praying for our enemies or persecutors. God shines the sun (literally, his sun) on them, gives them rain when it is needed. We have to realize that those whom we have reason to call our enemies, those who hurt or malign us, are living in darkness and are like parched and arid earth. When Jesus says love them and pray for them, He is saying: Be sun for them, be rain for them, give them light in their darkness, pray that they will be open to the transforming refreshment of grace. "For if you love only those who love you," He goes on, "what reward is there in that?" Anybody, even evildoers, can do that. You, however, are called to be children of the Father who gives sun and rain to all, deserving or undeserving. The final judgment is in his hands, and no one pulls the wool over his eyes, but this is the time for mercy, for generosity, for being the Father's hands and heart as He seeks to achieve his goal of salvation for all.
Be sun, then, and be rain, for the sake of those for whom Christ died. Be a child of your heavenly Father. Love and pray and go forth in peace, in the name of the Lord.