John Calvin, Institutes of the Christian Religion, III.4.6.696-7:
The great part of [men] are most unworthy if they be judged by their own merit. But here Scripture helps in the best way when it teaches that we are not to consider that men merit of themselves but to look upon the image of God in all men, to which we owe all honour and love. [You] say, ‘he is contemptible and worthless’; but the Lord shows him to be one to whom he has given the beauty of his image. Say that you owe nothing for any service of his; but God, as it were, has put him in his own place in order that you may recognise toward him the many and great benefits with which God has bound you to himself. Say that he does not deserve even your least effort for your sake; but the image of God, which recommends him to you, is worthy of your giving yourself and all your possessions. … You will say, ‘He has served something far different of me.’ Yet what has the Lord deserved? … remember not to consider men’s evil intention but … look upon the image of God in them, which … with its beauty and dignity allures us to love and embrace them.