The Lord commands all men without exception “to do good” [Heb. 13:16]. Yet the great part of them 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 honor and love. However, it is among members of the household of faith that this same image is more carefully to be noted [Gal. 6:10], in so far as it has been renewed and restored through the Spirit of Christ. Therefore, whatever man you meet who needs your aid, you have no reason to refuse to help him. Say, “He is a stranger”; but the Lord has given him a mark that ought to be familiar to you, by virtue of the fact that he forbids you to despise your own flesh [Isa. 58:7 Vg.]. Say, “He is contemptible and worthless”; but the Lord shows him to be one to whom he has deigned to give 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 recognize 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 his sake; but the image of God, which recommends him to you, is worthy of your giving yourself and all your possessions. Now if he has not only deserved no good at your hand, but has also provoked you by unjust acts and curses, not even this is just reason why you should cease to embrace him in love and to perform the duties of love on his behalf [Matt. 6:14; 18:35; Luke 17:3]. You will say, “He has deserved something far different of me.” Yet what has the Lord deserved? While he bids you forgive this man for all sins he has committed against you, he would truly have them charged against himself. Assuredly there is but one way in which to achieve what is not merely difficult but utterly against human nature: to love those who hate us, to repay their evil deeds with benefits, to return blessings for reproaches [Matt. 5:44]. It is that we remember not to consider men’s evil intention but to look upon the image of God in them, which cancels and effaces their transgressions, and with its beauty and dignity allures us to love and embrace them.
– John Calvin, Institutes of the Christian Religion, III, vii, 6.