Therefore you shall be perfect, just as your Father in heaven is perfect.  (Matthew 5:48)

Thee shall therefore be perfect. The first reference is to completeness in love to others; to an all embracing, instead of a narrow, exclusive affection.  But the highest virtue includes all the rest, since God is love.  We may then accept the correctness of the ordinary view, which understood the verse as setting up our heavenly Father (lit., ‘your Father, the heavenly one’) as the ultimate standard of our morality and holiness.  No other standard is allowable indeed.  Even the rendering we adopt implies a command to attain to this standard.  Our ability cannot affect the case.  ‘Likeness to God in inward purity, love, and holiness, must be the continual aim and end of the Christian in all the departments of his moral life.  But how far we are from having attained this likeness, St. Paul shows us (Philippians 3:12), and every Christian feels just in the proportion in which he has striven after it.’ (Alford.)  Instruction in morality cannot rise above this verse.  Christ alone can really give us such instruction, since He alone by life and death shows the perfection of God in man.  Having thus led us up to our Heavenly Father as the true standard, our Lord by a natural transition speaks next of our religious duties, i.e., duties to our Heavenly Father.