Be ye therefore perfect, even as your Father which is in heaven is perfect. Matt. 5:48.
"Therefore" is a key word in verse 48. It implies a conclusion to what has gone before.
This verse, with its call for Godlike perfection, needs to be connected with its context from verse 20 onward, but most specifically to verse 43 through 47, as a comparison of verse 45 with verse 48 will clearly demonstrate. Those are the only two verses in the entire chapter that summon Christians to be like their Father in heaven. Verses 43 through 47 make explicit the essence of that likeness.
Jesus is not dealing with abstractions here. Being like the Father means loving one's enemies, just as God loves His enemies. After all, doesn't He provide sunshine and rain for evil people (verse 45)? Anybody, even tax collectors and other unsavory sorts, can love their friends (verses 46, 47). But God loved the world that He gave His Son to die for people who were ungodly and His enemies, so are Christian to love even those who despitefully use them, "so that" they may be like their Father, "so that" they might be perfect, just as their heavenly Father is perfect.
That thought brings us to the word "perfect" in Matthew 5:48. Translated from the Greek word teleios, it has nothing to do with concepts of absolute sinlessness. To the contrary, teleios means "maturity," and in most instances most translations translate it as such.
In the Bible's use of the concept, people are teleios (perfect) when they are full-grown or have reached full stature. And for human beings that maturity means being restored to the likeness of God in whose image they were created. Thus it is only natural for Jesus to claim in Matthew 5:48 that the Christian should become teleios (perfect or mature) I love like the Father in heaven. After all, "God is love" (1 John 4:8). That is the essence of His perfection of character. Thus character perfection centers on acting in love like God rather than behaving like the devil.
Such an understanding of verse 48 lines up with its parallel in Luke, which reads" "Be merciful, even as your Father is merciful" (Luke 6:36, RSV). It also is in harmony with that forceful quotation on Christ's Object Lesson on perfectly reproducing the character of Christ (p. 69). The context makes it clear that such a reproduction centers on a "spirit of unselfish love and labor for others" (pp. 67, 68).
Father, help me today to be a loving person so that I might be like You.