The hadith of the man who prayed badly is often referenced, at least among Sunni schools, due to its clear descriptions of prayer; it describes, step-by-step, each of the mandatory forms of the regular salat.

The common narrations of this hadith do not, however, describe what mistake (or mistakes) were made in the original prayer to actually earn the reprimand "Go back and pray, for you have not prayed."

Is there any information available regarding these mistakes? Authentic sources are, of course, preferable, but anything from the hadith literature which sheds light on this event would be appreciated.