GIFT AND REQUEST
When we read Matthew 5.48--you are to be perfect as your heavenly Father is perfect--we might not even believe that is possible.  We might want to let that verse pour off of us like water off a rock.  But if Jesus said it, what He said must be true.

  How can we be perfect as God the Father, in heaven?  We are here, we are in our human life with the twisting strain of disappointments.  But Jesus must have meant something.
 
  We read in Acts that the Holy Spirit is given to men and women--we hear them in our own tongues speaking the mighty deeds of God, Acts 2.10.  It is by the power of this Spirit that the holiness of the Father is given to men and women.  But that is not all.  Having been given the gift to fulfill Matt. 5.48, God asks that we live out in that gift, that Spirit.

  We might say God gives a command for which He gives the gift, and then as we receive the gift God asks we live in it.

  Can we find an episode in the gospels which makes that plain?  I think we can look at John 8, the woman caught in adultery.  She is caught, throw down to dust in a corner of the temple courtyard.  The Pharisees and scribes surround her, to stone her as the Law proscribed, Leviticus 20.10.  Then they turn from her to Jesus, demanding of Him--what then do you say, John 8.5.  Jesus knows the Law.  And yet He knows she is a soul made in the image of God.  He knows the commandment against killing, Exodus 20.13.

  Here with this woman the Law is a rope unraveled in two directions, now so weakened so that it cannot be used.  One direction is to stone her, the other is to prevent killing her through forgiveness.  So Jesus must wrap the Law back together so that it glorifies God in heaven.  If the men stone her, they are taking the place of God in her death, without the hope of the resurrection since she will die without repentance.  If Jesus prevents the stoning of her, He must answer to the Law. 

  So He says the Pharisees and scribes cannot take the place of God to end her life.  He says they are not so perfect that they can cast the first stone--he who is without sin among you, let him be the first to throw a stone at her, John 8.7. 
  Jesus has made the demand of perfection mentioned in Matt. 5.48.  The Pharisees and scribes do not have such a gift, only Jesus does.  So He takes the gift from them to give it to her when He says--Woman, where are they?  Did no one condemn you, John 8.10.

  Having forgiven her, now Jesus tells her to live in the gift He has given her.  He tells her--Neither do I condemn you; go your way, from now on sin no more, John 8.13.  She has the gift of forgiveness so she must now live a new life in the holiness of Matt. 5.48.

  Most of the NT is about living out the gift we have been given, to be holy before the Lord.  All of the Sermon on the Mount is God's instructions on how to--sin no more.  This was always God's intention and will.  If we turn back to Exodus 20 (just 7 verses after the commandment against murder) Moses tells the people--do not be afraid for the Lord God has come in order to test you, and in order that the fear of Him may remain with you, so that you may not sin, Exodus 20.20.

  Our heavenly Father always desired holiness for us.  He gives what He requests in order to ask of us what He has given.  When He declares the request that we be holy, that is our justification.  When He gives the Spirit by which we can be holy, that is our sanctification.  It is majestic and it is for us, every one of us.

  Now having said that, how can it be?

  1 John 1.3 says--our fellowship is with the Father and with His Son Jesus Christ.  That we are complete in Him is stated in 1 John 1.7--If we walk in the light as He is in the light, we have fellowship with one another and the blood of Jesus His Son cleanses us from all sin...If we confess our sins, He is faithful and righteous to forgive us our sins nd to cleanse us from all unrighteousness.

 So we confess our sins, not because we are holy but to be holy.  John goes on to say--whoever keeps His word, in him the love of God has truly been perfected.  This is being holy by being cleansed of the sins we commit.  Confession of sins, keeping His word, loving God.
  Be holy as your Father in heaven is holy.