Therefore you shall be perfect, just as your Father in heaven is perfect. (Matthew 5:48)
Perfection is no arbitrary demand; in the very nature of things God can ask nothing less. And this is true whether we think of Him or ourselves….If we think of ourselves, the call to perfection is no less imperative (than God’s nature and Person being perfection). God is such an Infinite, Spiritual Good, and the soul is so incapable of receiving or knowing or enjoying Him except as it gives itself wholly to Him, that for our own sakes God’s love can demand of us nothing less than a perfect heart.