Its authorship is unknown. Several non-authoritative sources I found online suggested that it was composed in 10th-century Babylonia, or by Ibn Gabirol in 11th-century Spain. The more respectable sources I found generally did not suggest any attribution. It seems to have been added to the prayer services around the 16th century.
The first three stanzas are theological; the last two describe the believer's relationship to God. The last stanza begins with the words, "בידו אפקיד רוחי", "In his hand I entrust my spirit".
These words are a direct quotation from the New Testament.
I noticed this a few days ago in a news report about the Pope's death. I don't know how to take it. I can't be the only one who finds it strange that a supposedly Jewish prayer includes a line from the Christian Bible.
This brings us back to the question of authorship. The following possibilities suggest themselves to me.
- The resemblance is coincidental.
- The poem was written by a Jew who had read the Christian Bible and felt comfortable reusing its language in a Jewish context.
- The poem was written by a Christian, or perhaps a "Jewish Christian" who considered himself a traditional Jew but believed that Jesus was the Jewish Messiah.
- Part of the poem - the last stanza or two - was written by an author who drew on the Christian Bible, while the rest was written by one of the previously suggested authors. This would account for the presence of the line "והוא אחד ואין שני להמשיל לו להחבירה", "And he is one, and there is no second, to be compared to him, to be joined with him". While this line is not necessary a direct refutation of Christianity (Christians presumably think that they are in fact monotheists, believing in three aspects of one God), it does sound to me like anti-Christian polemic. However you read it, it's strange to see this and a Christian Bible quote located just four lines apart from each other. Perhaps this indicates that Adon Olam is an accretion of several authors' contributions, although the uniformity of the poem's meter (it's strict iambic pentameter all the way through) might indicate otherwise.