My ears often perk up at Christmas services when the angelic host's song in Luke 2.14 is read aloud in the beautiful text of the Authorized Version (AV): "Glory to God in the highest, and on earth peace, good will toward men". The AV was based partly on early printed editions of the Greek NT, for which the main available sources were late and poor Greek manuscripts of the NT. Erasmus, the editor of the first published edition of the Greek NT text (1516 and later), lacked both adequate Greek NT manuscript resources and time to use them, and could have no concept of the appropriate principles to govern a critical edition of the Greek NT. C.R.Gregory pointed this out long ago (Textkritik des NT, 1902, II, 928-931), and less trenchantly so did Metzger in his classic manual of NT textual criticism (2005 ed. by B.Ehrman). Although the AV is widely revered, sometimes the Greek text which is its basis disagrees with the results of modern scholarship.
As an aside, the usual Latin version, which was ubiquitous in the Western world and traces of which appear in many versions, can be translated as "Glory in the highest to God, and on earth peace among men of good will". This last phrase could be read to suggest (fairly reasonably) that peace is dependent on the attitude of men, an interpretation that is generally rejected as inconsistent with the theology of Luke.
Unfortunately, this passage (Luke 2.14) does not appear in the Greek texts of the NT which survive from the first three centuries of the Christian era, so scholars must rely on later sources, from the 4th century onward. They are well presented in the Nestle-Aland editions and in the United Bible Societies' editions of the Greek NT. Tischendorf, who in the 19th century added more to our knowledge of the Greek NT sources than any other scholar, reconstructed the now accepted Greek text of this passage from available sources (1869). The Revised Version (RV) of 1881, the revisors of which included F.J.A.Hort and B.F.Westcott, editors of the best critical British Greek NT text of the 19th century (also 1881), implied recognition of the correct Greek text. The RV had "Glory to God in the highest, and on earth peace among men in whom he is well pleased", noting Greek variants. Bruce Metzger in his textual commentary on the NT (1994) summarized the reasoning for accepting a Greek text which would correspond to something like the RSV "Glory to God in the highest, and on earth peace among men with whom he is pleased", which was modified to "among those whom he favors" in the NRSV.
Semitic equivalents of the Greek expression meaning "men of [his] pleasure", hypothesized on the basis of the reconstructed Greek text, have subsequently been found in Hebrew and Aramaic texts from Qumran. That such Semitic phrases underlay the Greek text had long been suggested, e.g. in Matthew Black's book on the Aramaic background of the gospels and Acts (3rd ed. 1967). I.Howard Marshall's (1978) commentary on Luke provides a scholarly overview.
Thus, we know beyond reasonable doubt what are the original text, meaning, and background of this passage in Luke. However, the uncomfortable thing is that the original reading of this passage is much less congenial in a UU context than is the later and corrupted reading. The later reading extends peace and good will to men in general; one could say that it is universalist, while the original text is more restrictive, and not as open-hearted.
Perhaps partly because of its implied universalism, this defective reading of the Authorized Version has left many traces in the English-language religious tradition, perpetuated in verse and song. To some it will seem that it is an inadvertent theological improvement, but if we wish to understand the origins and development of Christian thought, it is simply an accidental dead end.