Question: Why does Jesus tell us “to be perfect” when perfection, this side of heaven is impossible?
In both the Old and New Testaments, the words translated most often into English as “perfect” (Heb. Tamam; Gk. Telios) mean perfect in the sense of “complete,” “mature” or “finished.”
The word first appears in Scripture in Dt. 32:4, where it says of God, “He is the Rock, his works are perfect (tamam), and all His ways are just.” Here, the meaning of perfection emphasizes the sense of “complete” or “finished”—a reference to His completed work on day six of creation in Genesis, where all He made was declared “very good” (Gen. 1:31). As the Scripture says,
Heb. 4:3b …And yet his work has been finished since the creation of the world.
Elsewhere in the Old Testament tamam carries the idea of flawlessness:
2 Sam. 22:31 As for God, his way is perfect; the word of the LORD is flawless.
The last use of the word “perfect” in the Bible has to do with how a believer has “matured” spiritually in being governed by the love of God:
1 John 4:18 There is no fear in love. But perfect (mature) love drives out fear, because fear has to do with punishment. The one who fears is not made perfect (mature) in love.
In this case, being “made perfect” (telios) in love is viewed as a process in which some believers are further along than others. “Perfect” in this sense pictures a completed, finished process where the believer has come to full maturity in this matter of selfless love.
In a similar way, when Jesus says, “be perfect, therefore, as your heavenly Father is perfect,” He uses the word “perfect” in the sense of “spiritually mature.”
The word “therefore” makes it clear that Jesus is addressing a specific issue brought up in the preceding verses. Just before His statement about being perfect, Jesus challenges the popular saying among the Jews at the time, “Love your neighbor and hate your enemy” (Matt. 5:43). Instead, He says, those who truly want to be like God will “Love your enemies and pray for those who persecute you…” (Matt. 5:44). After all, He explains, God causes the sun and rain to benefit both the righteous and unrighteous (Matt. 5:45), so we should do likewise (46-47).
When it comes to your behavior in dealing with challenging interpersonal relationships, “Be perfect, (i.e., spiritually mature) therefore, as your heavenly Father is perfect (spiritually mature).”