Today's Gospel can dismay many a heart: "Be perfect as your Heavenly Father is perfect." Yikes! Jesus can't mean that, can he? I, for one, am mightily tempted to discount this command, except that I find it echoed in Paul, as well: "Be imitators of God as his very dear children."
I think the problem is that we Americans think perfection means "flawlessness" (my readers in other countries may not share this Puritan inheritance), and so it looks as though we are being commanded to be as flawless as the Godhead. (We will now pause for a spiritual panic attack.)
But Paul comes to the rescue, because being "imitators of God" sums up what came before: "Be kind to one another, compassionate, forgiving one another as God has forgiven you in Christ."
In fact, the whole section of Ephesians, from 4:2 through to almost the very end, can be read as a commentary on the Gospel phrase, "Be perfect as your Heavenly Father is perfect."