For some Bible scholars, Num 12:3 is a thorny verse: “Now the man Moses was very humble, more than any man who was on the face of the earth.” Biblical writers generally speak of themselves with ruthless, self-effacing objectivity. Their references to themselves lay bare their sins and failures. It is unlikely that a truly humble person would write in such a manner about himself, even if he actually felt the statement was true. Yet the Book of Numbers has traditionally been ascribed to Moses based on his writing activity (Num 33:1-2; Ex 17:14, 24:4, 34:27) and the assumption that the first five books of the Bible are a unit and come from one author.
However, it is not necessary to claim that the Book of Numbers came from Moses’ hand in final form. Portions of the book may have been added by scribes or editors from later periods of Israel’s history. This is also true for the Book of Deuteronomy in which the preamble (Deut 1:1-5) and the description of Moses’ death (Chapt. 34) were written by someone else. For example, Joshua was a likely contributor to various Books of the Torah based on Josh 24:26 which states: “And Joshua recorded these things in the Book of the Law of God.” (Kaiser et al., p 165)