"The Lord commands us to do 'good unto all men,' universally, a great part of whom, estimated according to their own merits, are very undeserving; but here the Scripture assists us with an excellent rule, when it inculcates, that we must not regard the intrinsic merit of men, but must consider the image of God in them, to which we owe all possible honour and love; but that this image is most carefully to be observed in them 'who are of the household of faith,' inasmuch as it is renewed and restored by the spirit of Christ. Whoever, therefore, is presented to you that needs your kind offices, you have no reason to refuse him your assistance.
"Say he is a stranger; yet the Lord has impressed on him a character which ought to be familiar to you; for which reason he forbids you to despise your own flesh. Say that he is contemptible and worthless; but the Lord shows him to be one whom he has deigned to grace with his own image. Say that you are obliged to him for no services; but God has made him, as it were, his substitute, to whom you acknowledge yourself to be under obligations for numerous and important benefits. Say that he is unworthy of your making the smallest exertion on his account; but the image of God, by which he is recommended to you, deserves your surrender of yourself and all that you possess.
"If he not only deserved no favour, but, on the contrary, has provoked you with injuries and insults,—even this is not just reason why you should cease to embrace him with your affection, and to perform to him the offices of love. He has deserved, you will say, very different treatment from me. But what has the Lord deserved? who, when he commands you to forgive all men their offences against you, certainly intends that they should be charged to himself."
—John Calvin, Institutes of the Christian Religion III.7, cited in Marilynne Robinson, When I Was a Child I Read Books (New York: Farrar, Straus and Giroux, 2012), 77-78