It took a brave Nahum Tate to include this song with fifteen others in a supplement to the hymnal with only words of Scripture for songs. At first rejected, the hymn has become a favorite to many. Knowing the background enhances my appreciation for the song. So he who knows the Old Testament appreciates all the more the New. So he who has read the prophets is better prepared to receive the Prince of Peace.
Any book is more appreciated when the reader knows the author.
That may explain why some people get so much from reading the Bible. There is a fourth reason why one does not hear what others hear. Sometimes we tend to hear what we want to hear. If it was a day he felt good, he took it as a compliment. If it was a day he felt inferior and incompetent, he took it as a complaint.