Matthew 5:47-48-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. 

With my wife being out of town for the past week and half, the foreseen task of taking my kids to all their activities triggers this immediate agitation, revealing my selfishness and immaturity of course.  Which is why I think God “laughs”, in always giving me such a task until my attitude gets better.  But the Lord is always faithful to show me why He engineers these times, because I get an opportunity to have some meaningful conversations with my kids along the way…(Deuteronomy 6:7)
My youngest daughter who is 8, had an interesting confession regarding this past Sunday’s sermon PH preached about the Good Samaritan.  She confessed by saying, “Daddy, you know when Pastor Hong said we are to love people we don’t like, that’s very hard!”  Which I then laughed, and told her, “not only is it hard, it’s impossible without God’s power to do so!”  I continued informing her of the reason we need Jesus, whose is perfect in demonstrating love.  Otherwise hatred reigns, usually through “the mask” of religious duties much like PH preached about…(Romans 5:8)
I realize when we are to be compared to God (like Jesus does in the passage I’m using), the immediate reaction can be to defend the horror of our sinfulness, which is revealed in different ways.  Either in pride, we justify that we are not to be compared to God, which contradicts what Jesus says in the passage.  Or we wrongly elaborate on grace, as if grace has no relation to making us comformed to the image of Jesus.  Instead we should let the “horror” of not being good enough, humble us to know that it is impossible to be godly without God empowering us to be, so we can’t boast in ourselves! (Romans 8:29, 2 Corinthians 3:18, Ephesians 2:8-9, 1  Peter 1:14-16)
The call to be perfect is supposed to make us overwhelmed, and know it’s impossible without God.  We know that even with the Holy Spirit, being perfect seems unreachable, but that is to reveal how weak and sinful we are, in desperation to need God to do the things He commands us to do!  Humbling us to a desperation for Jesus, not just for the power to do His will, but forgiveness for a lot of failure!  This will erase any idea that we can “achieve” our way to godliness.  This was what I trying to tear down in addressing my daughter, you need Jesus all the time, like your dad…  
The general argument I have heard to this truth, is that it will cause people to accept failure and stay in their sins, if they can’t “achieve” godliness.  The problem with such a person is their heart, not their sins.  If a person’s heart has no desire to please God because their sins, they probably don’t know and love God.  The goal of Christianity is to exalt Jesus Christ, not to see if we measure up as being “good enough”, we’re not, and if so Jesus died in vain.  If Jesus is the goal, than our sins will be confessed, and from His forgiveness we praise Him for His great love and mercy, which is the foundation of the Church.  So we are to strive for holiness, with a lot of failure surely, but Christ can be exalted in the grace to strive and the mercy to forgive sins/failure.  (Isaiah 64:6, Romans 6:1-2, Romans 15:8-12, Galatians 3:1-6, Ephesians 2:19-22, Hebrews 11:6)
In His Love, Ld