God's Attributes
Perfect
Perfection is the attribute of God that carries the concepts of being complete, sound, upright, and blameless. The idea of perfection is applied to God's knowledge (Job 37:16), His justice (Deut 32:4), His fidelity (2 Sam 22:31) and His promise keeping (Psalm 18:30). In addition, God's law is perfect (Psalm 19:7). When one speaks of God's perfection he is speaking of God being complete and whole. God lacks for nothing. Everything He says and does is complete and free from faults, demanding to be praised.
Just as God is perfect, believers are exhorted to be perfect. This generally means to be whole, mature (1 Cor 2:6; 14:20; Heb 5:14), or blameless (Gen 6:9) and upright (Prov 2:21). Mankind is to be found blameless and whole at each stage of his spiritual growth, meaning that sin is not be found. This is the goal of Christian growth. In the Old Testament this perfection in mankind came by observing the law (Psalm 119:1) but James makes it clear such perfection comes by steadfast faith.
James 1:4 (ESV)
And let steadfastness have its full effect, that you
may be perfect and complete, lacking in nothing.
Believers do not reach perfection. Paul admits to this (Phil 3:12), realizing that perfections comes as part of our glorification in the life to come (Phil 3:8-21), being a gift of Jesus (Heb 10:14). Thus, believers should understand the call to perfection is a call to sanctification, to growth in spiritual maturity. This is not a demand that Christian become "perfect" as God is perfect. Rather, Christians are to continuing growing in Christ to be found blameless at each level of development. They are to be living in Christ rather than to be a slave to sin.