Can Men Become Perfect in the Flesh?

Jesus teaches those who listen to him, “You have heard that it was said, ‘You shall love your neighbor and hate your enemy.’ 44 But I say to you, Love your enemies and pray for those who persecute you, 45 so that you may be sons of your Father who is in heaven. For he makes his sun rise on the evil and on the good, and sends rain on the just and on the unjust. 46 For if you love those who love you, what reward do you have? Do not even the tax collectors do the same? 47 And if you greet only your brothers, what more are you doing than others? Do not even the Gentiles do the same? 48 You therefore must be perfect, as your heavenly Father is perfect."

We must be perfect even as God is perfect? It's hard enough to love our enemies. Was Jesus kidding? Does he really expect us to be perfect? Is it true that we MUST BE perfect before we can ever see God face to face and enter the Kingdom of Heaven?