Saint Augustine, The City of God, Vol. II

I found what the prophet says: There is no joy for the wicked, says the Lord original: "Non est gaudere impiis, dicit Dominus"; as if the wicked could be "delighted" original: "laetari" rather than "rejoice" original: "gaudere" in their evils, because joy is properly the portion of the good and the pious. Likewise, that passage in the Gospel: All things whatsoever you would that men should do to you, do you also to them original: "Quaecumque vultis ut faciant vobis homines, haec et vos facite illis", seems to be said as if no one could wish original: "velle" or desire original: "cupere" anything evil or shameful. Consequently, due to the custom of speaking, some translators added the word "good" and translated it as: "All things whatsoever you would that men should do to you, do these good things to them." They thought it necessary to take care lest anyone should wish that shameful acts be done to him by men—to say nothing of baser things, at the very least, luxurious banquets—and then think that if he did the same to others, he would be fulfilling this commandment. But in the Greek Gospel, from which it was translated into Latin, "good" is not written, but: All things whatsoever you would that men should do to you, do you also to them; I believe this is because in the word "you would" original: "vultis", "good" was already intended to be understood. He did not say "you desire" original: "cupitis".

However, our speech should not always be constrained by these proprieties, but sometimes they must be used; and when we read those whose authority it is not lawful to resist, they are to be understood in a way that the right sense cannot find another outcome. Such are those things which, for example, I have mentioned partly from the prophet and partly from the Gospel. For who does not know that the wicked exult with delight? And yet: There is no joy for the wicked, says the Lord. Why is this, unless it is because "to rejoice" original: "gaudere" means something else when this word is set down properly and specifically? Likewise, who would deny that it is not rightly commanded to men that whatsoever they desire to be done to them by others, they should also do to them, lest they entertain one another with the shame of illicit pleasure? And yet it is a most salutary and true precept: All things whatsoever you would that men should do to you...