Jesus said in the Sermon on the Mount, “Be perfect, therefore, as your heavenly Father is perfect” (Mt 5:48).
This is often interpreted as a call to sinless perfection, something that Christians cannot attain prior to glorification. As such it’s used as a hermeneutical key to understanding the Sermon on the Mount as a whole. In this view, Jesus is not laying out the way of life for his followers. Instead, he is setting the bar so far out of their reach that they must turn to him for mercy and find acceptance in his righteousness.
I fully embrace the theological conclusions of this position: Christians cannot live sinlessly in this life and can only be accepted by God on the basis of the imputed righteousness of Jesus. However, I don’t think this text teaches that.
There are three reasons for understanding this verse as something that every Christian should and can obey.