perfect
The word implies full development, growth into maturity of godliness, not sinless perfection. (Ephesians 4:12-13). In this passage the Father's kindness, not His sinlessness, is the point in question. (Luke 6:35-36).
Related Commentaries of Matthew 5:48
Matthew 5:48
48 Be ye therefore perfect, even as your Father which is in heaven is perfect.