I regret to say, dear friends, that y'all are floundering about when there is a perfectly simple answer. I don't have it, since, alas, I am not a Hebrew scholar. What you quoted, Dr. Bill, is the classical English translation of a Hebrew psalm. To answer your question authoritatively, we need a Hebrew scholar to enlighten us on the Hebrew words for "rod" and "staff" in the original. Any scholars out there?